Interleukin-1β Inhibits in vitro Pulsatile Progesterone Secretion and Stimulates Prostaglandin F_2α Secretion by Micro-Retrodialyzed Baboon Corpus Luteum

Abstract

Interleukin-1β (IL-1β) modulates steroidogenesis and prostaglandin (PG) secretion by dispersed luteal cells of some non-primate species. To determine if IL-1β affects progesterone (P) and PGF_2α secretion by the baboon corpus luteum (CL), we microretrodialyzed the intact CL for 48 h; 12 h media (baseline), 12 h with IL-1β (3 IU/h), 12 h media only (post- IL-1β) and 12 h with cAMP (5 nmol/h). Four CL from the midluteal phase (LH + 8 days) were studied. P was measured by a sensitive and specific radioimmunoassay and PGF_2α by an enzyme immunoassay in the 10-min fractions of retrodialysates collected. P secretions were analyzed for peaks by PC Pulsar (3.0) and total P retrieved/12 h for each experimental segment was calculated. P secretion was pulsatile. Pulses of P declined from 8.2 ± 1.2/12 h (mean ± SEM) before to 5.0 ± 1.2 h after IL-1β treatment (P = 0.022), but increased to 10.2 ± 4.3/12 h with cAMP. Interpulse interval increased significantly from 92 ± 23 min (baseline) to 137 ± 31 min (p = 0.025) after IL-1β treatment. Total P secreted decreased significantly from 2471 ± 515 nmol/12 h (baseline) to 1480 ± 167 nmoles/12 h during IL-1β and 788 ± 85 nmoles/12 h after IL-1β (P = 0.015). P was immediately suppressed after starting IL-1β in 2 CL but declined only towards the end of treatment in the other 2 CL. PGF_2α secretion increased during IL-1β with a further increase after IL-1β, while P secretion was progressively inhibited. Therefore, IL-1β is luteolytic to the primate midluteal phase CL by inhibiting P while simultaneously stimulating PGF_2α secretion, demonstrating paracrine-autocrine interaction within the luteal tissue.

Key words

Baboon corpus luteum - Interleukin-1β - Progesterone - Microdialysis - In vitro