AJP - Endocrinology and Metabolism, Vol 250, Issue 3 282-E287, Copyright © 1986 by American Physiological Society
Functional changes in luteinizing hormone-secreting cells from pre- and postpartum ewes
M. E. Wise, H. R. Sawyer Jr and T. M. Nett
Luteinizing hormone (LH)-containing cells from ovine pituitaries obtained
during gestation and at various times after parturition were examined to
determine whether the ability to store and secrete LH in vitro was
correlated with morphological changes. Pituitaries collected on days 50 and
140 of gestation and on days 2, 13, 22, and 35 after parturition were
enzymatically dissociated and the resulting cells cultured in media
containing estradiol (12 pg/ml), cortisol (12 ng/ml), or no steroid. After
4, 7, or 10 days of culture, cells were washed and basal LH,
gonadotropin-releasing hormone (GnRH)-stimulated release of LH, and
cellular content of LH were determined. The content of LH (ng/10(6) cells)
was lowest on day 140 of gestation (2.7 +/- 0.3) and day 2 postpartum (2.2
+/- 0.6) and then increased (P less than 0.05) on days 13 (36.6 +/- 8.3),
22 (59.9 +/- 14.4), and 35 (54.6 +/- 19.3) postpartum. The percentage of
pituitary cells containing immunoreactive LH nearly doubled (P less than
0.05) between days 2 (5.6 +/- 0.2%) and 35 (10.6 +/- 1.1%) postpartum.
Moreover, LH-containing cells were smaller, and the percent total cellular
volume occupied by secretory granules was less on day 2 than on days 22 and
35 after parturition. Secretion of LH after 4, 7, or 10 days of culture
reflected the cellular content of LH and was not influenced by the presence
of steroids in the media. These data indicate that decreased synthesis of
LH during gestation is associated with hypoplasia of the LH-secreting
cells. These cells are reactivated during the postpartum period and their
capacity to synthesize LH gradually returns to normal.
