Nocturnal and diurnal levels of prolactin, LH, FSH, estrogens, and progesterone in middle-aged, spontaneously persistent estrous rats
Reproductive research in aging animals is often performed with very old rats manifesting spontaneous persistent estrus (SPE). However, Charles River (CD) Sprague Dawley rats present SPE as early as 6 months of age and thus are potentially very useful in such studies since the concomitant pathologies associated with old age can be avoided. Serum levels of LH, FSH, prolactin, estrogens, and progesterone were measured by RIA in 8 to 12 month SPE rats after rapid decapitation at 0300, 1000 or 1600 hr (8-11 rats/group). As reported by others in very old SPE rats, proiactin was high at 1600 hr (169±40 ng/ml) compared with levels at 0300 hr (43 ± 7 ng/ml) or 1000 hr (95 ± 25 ng/ml). LH and FSH values did not change with time of day, but those of FSH were consistently above baseline values of cyclic rats. Total estrogens were low (75 ± 9 pg/ml) at 1000 hr but significantly higher at both 0300 hr (127 ± 11.7 pg/ml) and 1600 hr (141 ± 23 pg/ml), resembling levels at about 1000 hr on proestrus in cyclic rats (125 ± 16 pg/ml). Average progesterone concentrations resembled baseline values of cyclic rats but varied widely (0.02 to 25 ng/ml). These findings suggest that the middle-aged SPE rat may be used in studies of the aging reproductive system, and that future studies with SPE rats should consider variations in prolactin, estrogen and progesterone with the time of day. © 1983 American Aging Association, Inc.
Beach, JE; Tyrey, L; Schomberg, DW; Everett, JW
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