LUTEOTROPIC EFFECTS OF FOLLICLE-STIMULATING-HORMONE (FSH) .1. FSH HASIN-VITRO LUTEOTROPIC AND SYNERGISTIC EFFECTS WITH LUTEINIZING-HORMONEAND PROLACTIN ON PROGESTERONE PRODUCTION BY HAMSTER LUTEAL CELLS DURING PREGNANCY

This study was designed to evaluate the in vitro ability of FSH, LH, a nd prolactin (PRL) to stimulate progesterone (P-4) production by enzym atically dispersed CL cells from pregnant hamsters. In light of previo us in vivo findings [1], we were especially interested in determining whether ESH is a luteotropin. The CL were collected and pooled on Days 4, 8, 12, and 16 of gestation (Day 1 = sperm-positive vaginal smear). After enzymatic dissociation, combined large and small luteal cells ( LC+SC) were incubated in the presence of 10 ng ovine to) FSH, oLH, and oPRL, alone or in various combinations, for a total of 144 h with the first medium change at 24 h and other changes every 48 h thereafter. FSH and LH alone significantly increased P-4 production on Days 4, 8, and 12, while PRC alone increased P-4 only on Day 12 (p < 0.05). The c ombination oFSH+oLH+oPRL significantly stimulated P-4 production on Da y 4 to a greater extent than the combination of any two hormones (P < 0.05). Ovine FSH+oLH enhanced P-4 production on Days 12 and 16 at 48, 36, and 144 h of incubation, to an extent greater than either hormone alone (p < 0.05). When recombinant human FSH (r-hFSH), which is devoid of LH activity, was added (1-100 ng) to dispersed luteal cells from D ay 4 pregnant hamsters, a dose-response increase in P-4 was evident (p < 0.05); even 1 ng r-hFSH stimulated P-4 production at 36 h (p < 0.05 ). On Day 2 of the cycle, oFSH or oLH, but not oPRL, also significantl y stimulated P-4 production (p < 0.05). LC showed more intense stainin g for 3 beta-hydroxysteroid dehydrogenase (SP-HSD) than did SC, and LC increased in number from 3.96% on Day 4 to 18.89% on Day 16; their di ameter also increased from 21 +/- 0.4 pm on Day 4 to 30 +/- 0.45 mu m on Day 12 (p < 0.05). Collectively, these experiments demonstrate that FSH is indeed a luteotropic hormone in the hamster and is involved in P-4 production throughout pregnancy. These results strongly support t he contention that a luteotropic complex exists in this species.