Ovarian development in young toads, Bufo bufo bufo (L.): Effects of unilateral ovariectomy, hypophysectomy, treatment with gonadotropin (hCG), growth hormone, and prolactin, and importance of body growth

Abstract

In young metamorphosed toads, Bufo bufo bufo, up to 15–20 g body weight, and about 6 cm body length, ovarian growth and development was mainly due to an increase in the number of oocytes. At this stage the total number in both ovaries amounted to about 30,000–40,000, the largest oocytes were about 0.35 mm in diameter, and the total ovarian weight was about 150–200 mg. During further development the number of oocytes remained constant, and ovarian growth was now due to growth of the oocytes. Unilateral ovariectomy in the young toads was followed within 2 months by a compensatory increase in number of oocytes in the remaining ovary that reestablished the number and size distribution of oocytes normal for two ovaries. This compensatory hypertrophy after unilateral ovariectomy depended upon body growth as measured by increase in length of the body. Inhibition of body growth of the unilaterally ovariectomized toads by reducing their food intake, or by hypophysectomizing the toads, prevented the compensatory growth of the remaining ovary. Treatment of hypophysectomized and unilaterally ovariectomized toads with growth hormone alone, or even better in combination with gonadotropin (hCG), restored body growth, and also the compensatory growth of the remaining ovary. Treatment with hCG alone had no effect on the number of oocytes, but did stimulate growth of some oocytes. Treatment with prolactin increased body weight, but not body length, and prolactin did not allow any compensatory ovarian hypertrophy. The nature of action of hCG on the ovary in immature toads is discussed.