The effects of a single injection of progesterone on the oestrous cycle, thyroid gland activity and uterus‐plasma concentration ratio for radio‐iodide in the rat

Abstract

SUMMARY1. A single subcutaneous injection of 5 mg, 1-25 mg or 625 ,tg, but not 312 jtg, of progesterone in oil delayed ovulation in the rat by 1 or more days, when injected at the dioestrous stage of a 4-day oestrous cycle.2. When ovulation was delayed in this way the expected increase in the thyroid-serum concentration ratio for 1311 was also delayed but the ratio did increase when delayed ovulation occurred.3. A single injection of progesterone resulted in an increase in the uterusplasma and oviduct-plasma concentration ratios for 1311; the increase was greatest when steroid was injected at the dioestrous stage of the cycle and was delayed and least when the steroid was given at the pro-oestrous stage. 4. Ovulation was advanced by 1 day when progesterone was injected on the second day of dioestrus in rats showing regular 5-day cycles; this ovulation was not accompanied by an increase in the thyroid-serum concentration ratio. In these experiments a dose of progesterone that failed to advance ovulation produced a rise in uterus-plasma and oviductplasma ratio for 1311 but no rise was seen when ovulation was induced, suggesting that oestrogen secretion had been stimulated. 5. 20a-Dihydroprogesterone (pregn-4-en-20ax-ol-3-one) was not effective in delaying or advancing ovulation at a dose level of 2-5 mg per rat and had no effect on the uterus-plasma concentration ratio for radio-iodide.6. These results are discussed in relation to the hypothesis that the increase in thyroid gland activity at the oestrous stage of the cycle is related to the neuro-endocrine changes that lead to ovulation.

Peroxidase-mediated Antimicrobial Activity of Rat Uterine Fluid

“…The uterus/plasma (U/P) ratio for I 131 has a mean value of 0.64 during the estrus cycle; however, on the 3rd and 4th day of either pregnancy or pseudopregnancy, the U/P ratio is greater than 1 suggesting the concentration of iodide by the uterus during this period [5]. Injection of progesterone during the estrus cycle produces a significant increase in the U/P ratio for iodide which is greatest during diestrus when values greater than 5 are observed [6]. Unlike the U/P ratio, the oviduct/plasma (O/P) ratio for I131 varied signifi cantly during the estrus cycle and was greater than 1 during metestrus and diestrus [5].…”

Regulation of Pituitary Ovulating Hormone Concentration in the Immature Rat Treated With Pregnant Mare Serum

“…Progesterone has been shown to inhibit, as well as to stimulate, ovulation in the adult rat (Everett & Sawyer, 1949 ;Rothchild & Schwartz, 1965 ;Hoffman & Schwartz, 1965;Zeilmaker, 1966;Brown-Grant, 1967;Caligaris, Astrada & Taleisnik, 1968), and this has led to the concept of a biphasic action of the hormone. In addition, progesterone has been shown to increase plasma LH (Nallor, Antunes-Rodrigues & McCann, 1966;Caligaris et al 1968) and to increase pituitary LH (Labhsetwar, 1969).…”

The Induction of Ovulation During Pregnancy in the Rat

“…When ovulation is delayed by the administration of progesterone but later occurs spontaneously, the usual increase in thyroid gland activity is seen in association with the delayed ovulation. In con¬ trast, when ovulation is advanced by progesterone in rats showing 5-day cycles, the usual increase does not occur (Brown-Grant, 1967a). Ovulation is suppressed during pregnancy in the rat and the periodic increases in thyroid gland activity in animals with regular cycles are also absent (Brown-Grant, 1965).…”