Influence of photoperiod and temperature on weight gain, food consumption, fat pads and thyroxine in male golden hamsters.

Weight gain in control and pinealectomized male golden hamsters is enhanced by exposure to short photoperiods (LD 8:16). Modest temperature reductions (10 degrees C) enhanced weight gain also, especially in the blinded animals. In the absence of both eyes and the pineal gland, neither temperature nor photoperiod had much or any effect on weight gain. Food consumption on the other hand increased only as a consequence of lowered temperature. Efficiency of food utilization was maximal at higher (22 degrees C) temperature and long photoperiods (LD 16:8). Epididymal fat pads in control animals were consistently increased by short photoperiods in either temperature. They were increased in pinealectomized and decreased in blinded animals as a consequence of lowered temperatures in either photoperiod. Total body weight gain in the several environments was not correlated directly with fat pad weights. Free thyroxine (T4) levels in control animals seemed to be negatively correlated with fat pad weights. Both T4 levels and fat pads were unchanged by temperature or photoperiod in blinded, pinealectomized animals. The data suggest a complex interaction of temperature, light and the pineal gland on body weight, fat deposition and serum T4.