EFFECTS OF INJECTION OF ANTI-LUTEINIZING HORMONE (LH)-RELEASING HORMONE SERUM AND ANTI-GONADOTROPIN-RELEASING HORMONE-ASSOCIATED PEPTIDE SERUM INTO NEONATAL RATS ON LH AND FOLLICLE-STIMULATING-HORMONE CELLS

Relatively little is known regarding the potential importance of LHRH and of gonadotropin-releasing hormone-associated peptide (GAP) on the postnatal development of gonadotrophs. We investigated the effects of administration of anti (A)-LHRH serum or A-GAP serum to neonatal rats on the development of LH and FSH immunoreactivity in anterior pituitar y gland (APG) cells. Serum (sheep non-immune [NSS], sheep A-LHRH, shee p A-LHRH/GAP [which bound LHRH and GAP], rabbit non-immune [NRS], or r abbit A-GAP) was injected s.c. into neonatal female and male rats on D ays 1 and 3 or Days 1, 3, 5, and 7 after birth. Pups were killed on Da y 5 or 9, two days after the last injection. The percentages of APG ce lls immunoreactive for LH or FSH increased from Day 1 to Day 5 and did not change between Days 5 and 9 in female pups treated with NSS or NR S. There was a trend for the percentages of LH and FSH cells to increa se from Day 1 to Days 5 and 9 in male pups treated with NSS or NRS, bu t the increases were not statistically significant. In both females an d males, treatment with antisera that recognized LHRH reduced the perc entage of FSH cells on Day 5 and the percentages of LH and FSH cells o n Day 9. Treatment with A-GAP was without effect in both sexes. There were similar percentages of LH and FSH cells in females and a lower pe rcentage of FSH than of LH cells in males in the Day 5 and 9 controls. In females, administration of antisera that recognized LHRH resulted in a lower percentage of FSH than of LH cells on Days 5 and 9. LH and FSH cell size did not change from Day 1 to Day 5 or 9 in controls of e ither sex. In females, administration of antisera that recognized LHRH decreased the size of FSH cells an Days 5 and 9, and A-LHRH/GAP decre ased the size of LH cells on Day 9. A-GAP had no effect in females, an d no treatment had any significant effect on the size of LH or FSH cel ls in males. LH and FSH cell sizes were not different within any group of either sex. The results indicate that LHRH but not GAP plays a rol e in the development of the percentage of APG cells with LH or FSH imm unoreactivity in the APG of female and male rats and affects the size of gonadotrophs in female rats. The results also suggest that, at leas t in females, LHRH is important for maintaining FSH synthesis in gonad otrophs.