Non-genomic rapid responses via progesterone in human peripheral T cells are not indirectly mimicked by sphingosine 1-phosphate.

•Progesterone membrane receptors (mPRs) are classified as progestin and adipoQ receptors (PAQRs).•Being alkaline ceramidases, mPRs convert ceramide to sphingosine then by phosphorylation to sphingosine 1-phosphate (S1P).•Rapid responses by progesterone involve [Ca2+]i elevation and acidification.•S1P stimulates [Ca2+]i elevation but causes neither acidification nor the suppression of PHA induced proliferation.•The rapid responses induced by progesterone probably do not involve indirect signaling via S1P/S1PRs.