Individuals with mitral valve prolapse (MVP) frequently show symptoms of a hyperadrenergic state.βadrenergic receptor characteristics were compared in the lymphocytes of subjects with symptomatic MVP and control subjects during rest and exercise. At rest, the proportion of receptors binding agonist with high affinity, as determined from isoproterenol competition for (—)[125I]-iodopindolol binding sites, was greater in MVP subjects than in controls. With exercise, the proportion of high-affinity receptors in MVP subjects decreased to control levels. Isoproterenol stimulation of lymphocyte 3’, 5’-cyclic adenosine monophosphate (cyclic AMP) also was greater in MVP subjects than in controls at rest, but not during exercise. Plasma catecholamine concentrations in MVP subjects were normal during both rest and exercise. Unlike exercise, isoproterenol infusion elicited clinical manifestations of increased adrenergic responsiveness in MVP subjects. Theβreceptor in exercised MVP subjects exhibited unusually high affinity agonist binding (i.e. a lower dissociation constant KHthan in either the same subjects at rest or exercised controls) and also abnormal coupling to the stimulatory guanine nucleotide-binding regulatory protein (GS) of adenylate cyclase, as reflected by the inability of guanine nucleotide to convert the receptor to a low-affinity state. These findings suggest that functional alteration of theβadrenergic receptor, in the absence of abnormal plasma catecholamine levels, might contribute to the hyperadrenergic state of MVP subjects at rest. However, desensitization of high affinityβreceptors or altered receptor-Gs coupling might preserve normal adrenergic responsiveness during exercise.

Modern computer design offers the opportunity to rapidly and objectively analyze the large quantity of data obtained during prolonged intraesophageal monitoring. The purpose of this study is: (1) to describe a rapid automated technique for acquisition and analysis of esophageal parameters, using a microcomputer; and (2) to compare computerized versus manual analysis of physiograph recordings. Ten normal subjects underwent 24-hr computerized monitoring of intraesophageal function, including: (1) pH recording at 5 and 10 cm above the lower esophageal sphincter (LES); (2) pharyngeal contraction; (3) esophageal contraction at 5 and 10 cm; (4) posteriorly directed LES pressures; and (5) gastric pressure. Segments from several studies were chosen for comparison of physiograph data with that obtained by computer. No significant differences were found except for the number of esophageal contractile events. This difference stems from a problem of shifting baseline related to subject position. Thus, the computer can be used for analysis of large quantities of data obtained from prolonged esophageal monitoring.