Effects of Norethynodrel and Mestranol on Pituitary Luteinizing Hormone in the Female Rat

Studies on the Mode of Action of Oral Contraceptives: Effect of Chlormadinone on Pituitary FSH and Lh Contents of the Female Rat

“…However, ovaries of immature pseudopregnant rats treated with this progestagen were as sensitive to the ovarian-ascorbic-acid-depleting activity of exogenous lh as those of the controls. Furthermore, ovaries in rats (Harper, 1964) and rabbits (Rudel & Kind, 1966) Labhsetwar, 1967a;Schwartz & Rothchild, 1964), while progesterone (Everett, 1964) as well as synthetic progestagen-norethynodrel (Labhsetwar, 1966a) have been found capable of inducing pseudopregnancy in the rat.…”

“…Although it is likely that the total effectiveness of these agents probably results from their action at multiple sites in the body (such as the ovary, uterine tubes, uterus, cervix, pituitary and hypothalamus), their primary action is believed to be exerted at the pituitary-hypothalamic level, inhibiting the output of luteinizing hormone (lh) and consequently ovulation (Vorys, Ullery & Stevens, 1965;Flowers, Vorys, Stevens, Miller & Jensen, 1966). Previously it has been reported that prolonged administration of a progesterone derivative, Provera, results in depletion of pituitary lh stores (Labhsetwar, 1966b), while the administration of a 19-nor steroid derivative, norethynodrel, for a period of 10 or less days was found to result in a significant increase in the pituitary lh content of the female (Labhsetwar, 1967b) as well as the male rat (Brown, Wells & Youngson, 1965).…”

The Influence of Norethynodrel on the Hypophysis

“…Similar disagreement exists regarding the influence of norethynodrel on pituitary weight, no change (1,(3)(4)(5) and an increase ( 2 ) having been reported. However, the extensive evidence that norethynodrel stimulates the secretion of prolactin (6)(7)(8)(9)(10) and, depending on the dose level, either elevates the gland content of luteinizing hormone (LH) (11,12) or reduces the content ,of total gonadotropin (5) indicates that significant alteration in pituitary cytology is to be expected. Determination of the pituitary cytological response to norethynodrel is of special interest because it has both progestational and estrogenic (4) properties and little is known about the combined action of naturally occurring progestins and estrogens on pituitary cells.…”