The effects of acclimation temperature on pituitary and plasma beta-endorphin in rats at 32.5 degrees C.
Endocrine and thermoregulatory responses were studied in male rats exposed to heat (32.5 +/- 0.1 degrees C) from acclimation temperatures of either 24.5 +/- 0.1 degrees C or 29.2 +/- 0.1 degrees C. After 1 hr in the heat, evaporative water loss and tail skin temperature changes in the 24.5 degrees C acclimated rats were greater than in the 29.2 degrees C acclimated rats; both groups displayed similar changes in metabolic rate and rectal temperature. At the respective acclimation temperatures, 29.2 degrees C rats displayed lowered plasma thyroid hormones, elevated beta-endorphin-like immunoreactivity (beta-END-LI) in the plasma, neurointermediate and anterior lobes of the pituitary gland, and no change in plasma corticosterone levels compared to 24.5 degrees C rats. After exposure to 32.5 degrees C for 1 hr, both groups of rats maintained similar plasma corticosterone levels; however, only the 24.5 degrees C group increased plasma thyroxine and beta-END-LI. These data suggest that beta-endorphin may be involved in body temperature regulation during acclimation to elevated environmental temperatures.
Gwosdow
A R
AR
Besch
E L
EL
Chen
C L
CL
Li
W I
WI
D000064:Acclimatization; D000818:Animals; D001831:Body Temperature; D001833:Body Temperature Regulation; D003345:Corticosterone / Q000097:blood; D004723:Endorphins / Q000097:blood / Q000378:metabolism*; D008297:Male; D010101:Oxygen Consumption; D010902:Pituitary Gland / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013696:Temperature; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood; D001615:beta-Endorphin
D004723:Endorphins; D014284:Triiodothyronine; D001615:beta-Endorphin; D013974:Thyroxine; D003345:Corticosterone