Effect of luteinising-hormone in vivo on ovarian cell subpopulations of newly-hatched chicks

1. We analysed the number and size of different ovarian cell subpopulations of newly-hatched chicks bl; ovarian cell suspension count and morphometric /stereological methods as well as Delta (5)-3 beta -hydroxysteroid dehydrog enase (Delta (5) -3 beta HSD) activity in these cells created in vivo with LH during embryonic development. 2. Fertile White Leghorn eggs received 1 mug LH applied to the chorioallant oic membrane on days 13, 15, and 17 of incubation. All animals were killed within 2 1 h after hatching, the left ovary was dissected and processed. 3. The results indicate that the number of germ, pregranulosa, interstitial and undifferentiated cells was not affected by LH treatment. However, we o bserved an increase in the size of individual interstitial cells of the ova rian medulla. In these cells, Delta (5) -3 beta HSD activity was increased in response to LH. 4. These findings suggest that LH does not exert a proliferative effect on the cells of tie prefollicular ovary of the chick and that interstitial cel ls can be target cells for LH, increasing their steroidogenic activity due to LH treatment.