The metabolic effects of dopamine have been investigated by its infusion in normal man with and without simultaneous somatostatin administration. Dopamine was infused into overnight fasted men at 1.5 µg/kg/min (n=6) and 3.0 µg/kg/min (n=5) for 120 min. Plasma dopamine concentrations at 120 min were 78±9 nmol/l and 117±17 nmol/l respectively, associated with a marginal rise in plasma noradrenaline. Dopamine (1.5 µg/kg/min) induced an early and sustained rise in plasma glucagon (48±9 pg/ml versus 19±6 pg/ml in saline controls at 10 min, p<0.01)and a transient elevation in serum growth hormone which peaked to 17.7 (range 4.5–71.8)mU/l at 60 min (7.2 (range 0.6–37.7) mU/l with saline, p<0.05), but did not alter serum insulin, blood glucose or other metabolite levels. At 3.0 µg/kg/min, dopamine in addition provoked mild and transient elevations in blood glucose and serum insulin. Somatostatin (250 µg/h) suppressed circulating insulin, glucagon, and growth hormone levels and abolished the small hyperglycaemic effect seen with the higher dopamine dose. Somatostatin alone induced a progressive rise in circulating non-esterified fatty acid and 3-hydroxybutyrate levels reflecting insulin deficiency. This rise in NEFA and 3-hydroxybutyrate was increased by dopamine particularly at the higher dosage (plasma NEFA; somatostatin alone, 1.08±0.13 mmol/l; somatostatin plus dopamine 3 µg/kg/min, 1.44±0.17 mmol/l at 120 min, p<0.01: blood 3-hydroxybutyrate; somatostatin alone, 0.32±0.04 mmol/l; somatostatin plus dopamine 3 µg/kg/min, 0.56±0.12 mmol/l at 120 min, p<0.05). Thus: 1) dopamine at pharmacological dosage has minor effects when other endocrine mechanisms are intact, 2) it enhances lipolysis and ketogenesis during somatostatin-induced insulin deficiency, 3) the hyperglycaemic effect of the higher dopamine dose is probably mediated through stimulated glucagon secretion.

Surgical trauma is a stimulus for the acute-phase response (APR), which is thought to be mediated by cytokines such as interleukin-6 (IL-6) (1). Features of the APR include changes in plasma concentrations of proteins such as C-reactive protein (CRP) and albumin and a lowering of plasma Zn and Fe concentrations (2). The metallothioneins (MTs), a family of metal-binding proteins, are also likely to be increased during the APR. Indeed, MT-1 and MT-2 genes are responsive to a wide variety of stimuli, including metals, cytokines, glucocorticoid hormones, and stress (3)(4). We previously reported a sevenfold increase in circulating MT-1 concentrations 24–48 h after elective surgery (5), confirming observations in animal experiments that MT can act as an acute-phase reactant (6)(7). We also previously showed (8) that extradural anesthesia added to general anesthesia resulted in lower concentrations of cortisol and growth hormone than did general anesthesia alone, but IL-6, CRP, and Zn concentrations did not change significantly. Here, we have investigated the time course of the changes in plasma concentrations of MT-1, CRP, and IL-6 in patients undergoing elective surgery. We also studied the effects of extradural blockade in addition to general anesthesia. Because MT is induced …

The role of calcitonin and parathyroid hormone (PTH) in corticosteroid-induced osteoporosis is controversial. We therefore measured plasma calcitonin and PTH levels in 34 adults receiving chronic pharmacological corticosteroids for obstructive airways disease, and in controls matched for age, sex, menopause, and disease. In addition, the acute effect of a 7-day course of 15 mg prednisolone daily on fasting and calcium-stimulated calcitonin was studied in 10 normal male volunteers. There was no difference in calcitonin and PTH levels in the corticosteroid-treated patients when compared with controls. The corrected serum calcium was significantly higher in the steroid-treated patients (patients mean 2.40 (SEM 0.01) mmol/liter; controls mean 2.33 (SEM 0.01) mmol/liter; P < 0.001). The short course of corticosteroids in volunteers did not alter basal or stimulated calcitonin, PTH, or calcium levels. These results suggest that neither calcitonin deficiency nor PTH excess is a feature of corticosteroid-induced osteoporosis.

Although the peptide content of endocrine cells is reliably demonstrated by immunocytochemistry, it may be unrelated to the immediate physiological state of the cell and the turnover rate of cellular products. By studying the mRNA present in the cytoplasm by in situ hybridization, it is possible to evaluate the synthetic activity of a cell. Although the cytoplasmic mRNA content is dependent on factors such as the rate of post-transcriptional processing and mRNA stability as well as on the rate of formation of primary gene transcripts (1), in situ hybridization of mRNA is still a useful technique for comparing changes in physiological activity. Our hypothesis was that the combination of immunocytochemistry and in situ hybridization might provide a more complete picture of the dynamic endocrinology of a tissue. Prolactin and POMC gene expression in rat pituitary were used as examples. We studied prolactin synthesis and secretion during pregnancy and lactation, and also after ovariectomy, because estrogen is known to stimulate the synthesis and secretion of prolactin in vivo and in vitro (2,3), such regulation taking place at the level of prolactin gene transcription (4,5). Prolactin mRNA levels increase in pituitaries of normal rats or hypogonadal mice given estrogen treatment (6,7). The technique of in situ hybridization has already been used to demonstrate increased prolactin mRNA in sections of pituitary from rats given chronic diethylstilboestrol treatment (8) or estrogen (9).

We have investigated the use of in situ hybridisation together with immunocytochemistry for the study of endocrine cell function, using as an example the expression of prolactin messenger RNA (mRNA) in pituitaries of rats under various endocrinological conditions. In situ hybridisation using a 32P-labelled cRNA probe for rat prolactin was carried out on sections of 4% paraformaldehyde-fixed pituitaries from prepubertal, pubertal, pregnant, lactating and ovariectomised rats and adjacent sections were immunostained for prolactin. Northern gel analysis was performed on total RNA extracts of pregnant, lactating and control pituitaries. While in ovariectomised rat pituitaries both prolactin immunoreactivity and prolactin mRNA were decreased, no differences in prolactin immunostaining were seen between prepubertal, pubertal, pregnant or lactating rats and controls, even when the supra-optimal dilution technique was used. However, using in situ hybridisation, prolactin mRNA signal was increased in prepubertal rats, and with hybridisation and northern gel analysis the signal was reduced in pregnant rats and markedly increased in lactating rats. The combined use of in situ hybridisation and immunocytochemistry provides morphological information concerning endocrine gene expression and protein synthesis in the pituitary gland.

The distributions of three novel peptides, 7B2, neuromedin B, and neuromedin U, in rat, mouse, and human pituitaries, rat hypothalamus, and 30 human pituitary tumors were investigated with immunocytochemistry. Immunoreactivity for 7B2 was present in rat, mouse, and human gonadotropes, in intermediate lobe cells and posterior lobe nerve fibers in rats and mice, in rat hypothalamus (particularly in the median eminence), and in eight human pituitary gonadotropinomas. In gonadectomized rats, larger, more numerous LH beta- and 7B2-immunoreactive gonadotropes were seen than in controls. Extractable 7B2-like immunoreactivity was elevated but not significantly so in gonadectomized rat pituitaries [males: castrated, 37.4 +/- 4.3 (mean +/- SE); controls, 26.9 +/- 4.3; females: ovariectomized, 27.2 +/- 2.7; controls, 19.1 +/- 2.2 pmol/gland]. Neuromedin B immunoreactivity was found in normal rat and mouse thyrotropes and weakly in "thyroidectomy" cells in hypothyroid rats, in which extractable pituitary neuromedin B was significantly depleted (thyroidectomized, 87.0 +/- 14.0; methimazole-treated, 82.0 +/- 11.4; control, 230.7 +/- 25.6 fmol/gland). Hyperthyroid rat pituitaries showed increased TSH beta and neuromedin B immunoreactivities and neuromedin B content (TRH-treated, 385.2 +/- 30.2; T4-treated, 352.6 +/- 20.2; control, 230.7 +/- 25.6 fmol/gland). Neuromedin U immunoreactivity occurred in corticotropes of all species, in rat and mouse intermediate lobe, and throughout the rat hypothalamus, with immunoreactive cell bodies in the arcuate nucleus. Neuromedin U-immunoreactive cells were present in six of six human pituitary and five of six human extrapituitary corticotropinomas. In adrenalectomized rats, corticotropes were larger and more numerous than in controls, but extractable anterior pituitary neuromedin U-like immunoreactivity was not raised (adrenalectomized, 3.30 +/- 0.45; control, 3.32 +/- 0.27 pmol/gland). Our findings suggest that 7B2, neuromedin B, and neuromedin U may be involved in pituitary function.

Infusion of the three human prepro-VIP derived peptides [vasoactive intestinal peptide (VIP), peptide histidine methionine (PHM) and the newly discovered peptide histidine valine (PHV-42)] at a constant nominal rate of 5 pmol/kg/min in 6 healthy volunteers for 60 min resulted in plateau plasma levels of 56,475 and 1,052 pmol/l, respectively. Although these values were above those found in the circulation under physiological conditions, only VIP caused a significant rise of prolactin (PRL) during, and postinfusion. Circulating luteinizing hormone and cortisol concentrations remained unchanged. As peptide histidine isoleucine, the porcine equivalent of PHM, has been postulated to be a potent hypophyseal portal pituitary PRL-releasing factor in the rat, we suggest that in man, VIP is more active than either PHM or PHV-42, and is likely to be a better candidate.

A group of 22 newly diagnosed noninsulin-dependent diabetic subjects and seven nondiabetic subjects underwent a glucose clamp at plasma glucose 100 mg/dL with insulin infusion rates of 1.0 and 10 mU/kg/min. During both insulin infusion rates, there was a sustained rise in plasma growth hormone (GH) above basal in 18 of the 22 diabetic subjects. Basal GH values were 2.37 ± 0.67 ng/mL, rising above basal during the lower insulin infusion (6.1 ± 3.3 ng/mL, P = 0.05) with a further rise at the higher insulin level (8.58 ± 2.0 ng/mL, P < 0.001). There was no rise in GH in any of the nondiabetic subjects. In neither group was there any rise above basal in cortisol, prolactin, glucagon, or somatostatin (SRIH). In a group of three nondiabetic subjects, a rise in GH similar to that seen in the diabetic group was induced by elevating the plasma glucose to 200 mg/dL for 60 minutes prior to the euglycemic clamp procedure. However, it is unlikely that changes in plasma glucose account totally for the changes in plasma GH described in the diabetic subjects since a rise in plasma GH was also seen in four diabetic subjects clamped at their fasting plasma glucose. We conclude that in newly diagnosed noninsulin-dependent diabetic subjects there is a rise in plasma GH during the euglycemic clamp procedure, which may be due to both the prior lowering of plasma glucose and the high plasma insulin levels.

The spontaneously diabetic Wistar rat (the BB rat) develops a dia betic syndrome which has many affinities with human insulin-dependent (Type 1) diabetes ( Marliss, Nakhooda, Poussier and Sima 1982). In these animals the onset of disease is remarkably rapid and characterised by hyperglycaemia, glycosuria, ketonaemia and hypoinsulinaemia. All these studies have been carried out on untreated rats followed until their condition dictated sacrifice, usually no longer than 40 days post onset of the disease. There is no data available on changes in circulating metabolite concentrations in these animals on insulin treatment. If the BB rat is to be used as a model for human Type 1 insulin-dependent diabetes, study of the characteristics before and at onset of diabetes is vital but valuable information may also be gained from studying these animals on life long insulin treatment.

The effects of two differing concentrations of halothane, 2.1 MAC or 1.2 MAC, on the metabolic and endocrine responses to abdominal hysterectomy were investigated. The changes in blood glucose and lactate values, and plasma glycerol, cortisol, insulin and catecholamine concentrations were similar in both groups. We conclude that high concentrations of halothane do not suppress the responses to pelvic surgery, and that accurate quantification of the dose of halothane, within the concentration range of 1.2 to 2.1 MAC, is not essential in studies of metabolic changes associated with surgery.