DIFFERENTIAL SENSITIVITY OF CELLS OF FOLLICULAR EPITHELIUM AND OOCYTES IN THE STELLATE STURGEON TO UNFAVORABLE CONDITIONS, AND CORRELATING INFLUENCE OF TRIIODOTHYRONINE

In experiments in which prior to the onset of maturation adult females of the stellate sturgeon were cooled or kept in prolonged captivity (reserved), or in which isolated ovarian follicles were exposed to extremes of temperature, the cells of the follicular epithelium lost their capacity to respond to hypophysial hormones as shown by the failure of the oocytes to mature after hormone treatment. On the other hand, in the same conditions exogenous progesterone was able to induce in vitro maturation of oocytes. Injections of triiodothyronine into females after cooling or reservation restored the ability of the follicular cells to respond to hypophysial hormones by stimulation of oocyte maturation. The significance of this action of thyroid hormone in the reproductive physiology of the fish is discussed. © 1979.