A ROLE FOR TESTOSTERONE IN THE MAINTENANCE OF SEASONALLY APPROPRIATE BODY-MASS BUT NOT IN LIPECTOMY-INDUCED BODY-FAT COMPENSATION IN SIBERIAN HAMSTERS

The purpose of this study was to test whether serum testosterone (T) c oncentrations characteristic of reproductively active, long-day-housed Siberian hamsters are necessary for compensatory increases in nonexci sed fat pads following removal of epididymal white adipose tissue (EWA T) and/or for the maintenance of seasonally appropriate body weights i n these hamsters. Long-day-housed hamsters were castrated or left inta ct, sham or EWAT lipectomized, and given T or cholesterol (C) implants . All groups had ad libitum food access except for two castrated T-tre ated groups that were pair-fed to their C-treated counterparts to cont rol for effects of T on food intake. C-treated castrates had decreased body weights compared with all other groups, suggesting a role of T i n the maintenance of seasonally appropriate body mass. Since the T-tre ated hamsters pair-fed to these T-deficient animals exhibited seasonal ly appropriate body weights and fat pad masses, T does not appear to a ffect these parameters through the modulation of food intake. All fat pads of C-treated animals were smaller than those of ad libitum- or pa ir-fed, T-treated castrates; however, EWAT was the only fat pad that w as smaller in the C-treated sham-lipectomized group than in gonad-inta ct sham-lipectomized hamsters. This result may indicate an enhanced se nsitivity of EWAT to T. The effects of T on fat pad mass were not asso ciated with proportionate changes in lipoprotein lipase activity, sugg esting that the major effect of T on fat accumulation occurs through o ther mechanisms in this species. C-treated lipectomized hamsters compe nsated for the body fat deficit 8 weeks after lipectomy via statistica lly nonsignificant increases in retroperitoneal and inguinal WAT mass. This finding suggests that, whereas T is necessary for maintenance of seasonally-appropriate body weight, it is not necessary for fat pad c ompensation after EWAT lipectomy.