PARENT SESSION
Follicular Development
120
CIRCULATING LEVELS OF LEPTIN, INSULIN, ESTRADIOL, ANDROSTENEDIONE AND LUTEINIZING HORMONE: RELATIONSHIP WITH BODY MASS AND OVARIAN MORPHOLOGY IN SHEATH-TAILED BAT, Taphozous longimanus .
Singh, Udai1, Krishna, Amitabh2, Sridaran, Rajagopala1, 1 2
ABSTRACT- The pattern of follicular growth, ovulation and concentrations of steroid hormones were studied during reproductive cycle in the sheath-tailed bat, Taphozous longimanus. Serum concentrations of leptin, insulin, androstenedione, luteinizing hormone (LH), and estradiol were measured by radioimmunoassay. T. longimanus breeds twice in quick succession in a year. The ovarian recrudescence was noticed during September and antral follicles were first observed in October. These changes in the ovary were associated with simultaneous increase in estradiol and androstenedione concentrations. Antral follicles in the ovary grew slowly during the period of high androstenedione levels from October to December. Leptin levels reached a peak in December (24.5±2.3 ng/ml) corresponding to a peak in androstenedione levels (98.2±3.4 ng/ml). Thereafter leptin levels declined during other months of the year. A positive correlation was observed between serum leptin, insulin and androstenedione levels prior to first pregnancy. Serum insulin levels attained a peak in December (122.8±4.2 iu/ml) and remained low during other months of the year. A dramatic drop in androstenedione levels was noticed in January, which coincides with a peak in estradiol (326.6±4.7 pg/ml) and LH (86.9±5.2 iu/ml) levels. The number of antral follicles increased in the ovary during this period. Subsequently, one of the follicles ovulated in January and first pregnancy began. T. longimanus exhibits alternation of ovulation between two ovaries in two successive pregnancies. During second pregnancy, antral follicles appeared in the contralateral ovary, which had no corpus luteum. The follicular growth was quite rapid and they soon attained the preovulatory status. This was apparent from the sharp increase in estradiol (283±3.4 pg/ml) and LH (93.4±3.1 iu/ml) levels. These results suggest that high levels of androstenedione and leptin from October to December retard follicular growth and delay ovulation. The high levels of leptin and insulin maintain reproductive activity in adverse environmental conditions during winter dormancy. (Supported by grants SO6-GM08248 from NIH and NAG 9-963 from NASA to RS and SP/SY/06/1999 from DST, India to UPS).
KEY WORDS: Bat, Ovarian cycle, Leptin, Androstenedione