Charles H. Spilman

Inhibition of platelet thromboxane A2 synthase activity by sodium 5-(3′-pyridinylmethyl)benzofuran-2-carboxylate

This report outlines the activity of a new thromboxane synthase inhibitor sodium, 5-(3-pyridinylmethyl)-2-benzofurancarboxylate, (U-63557A). U-63557A is a potent inhibitor of the thromboxane synthase in human platelets in vitro, as well as in rhesus monkey platelets ex vivo. A single oral dose of 3.0 mg/kg U-63557A inhibits the platelet thromboxane synthase in rhesus monkeys approximately 80% for at least 12 hrs. U-63557A has been administered to monkeys twice a day, (10 mg/kg) for 14 days, without evidence of drug tachyphylaxis or rebound. U-63557A does not inhibit thrombin-stimulated PGI2 biosynthesis in human endothelial cells, the 5-lipoxygenase in human neutrophils, or the cyclo-oxygenase in a variety of test systems. In anesthetized dogs, U-63557A injected i.v. at 0.1 to 5 mg/kg prevented the blockage of stenosed coronary arteries caused platelet aggregation. Similar effects were obtained by oral administration of 1-5 mg/kg. The thromboxane synthase inhibitor was more efficacious than cyclooxygenase inhibitors and equal to PGI2 in efficacy. Under appropriate conditions the protective effects of U-63557A could be reversed by i.v. cyclooxygenase inhibitors suggesting that its efficacy depended in part on endogenous PGI2 formation. Due to its specificity, oral activity, and extended duration of action, U-63557A is a promising compound for the evaluation of the role of thromboxane synthase in a variety of pathophysiological states.

Pioglitazone hydrochloride inhibits cholesterol absorption and lowers plasma cholesterol concentrations in cholesterol-fed rats

Diabetes is associated with altered cholesterol metabolism that may contribute to cardiovascular complications. Treatment of rats with pioglitazone hydrochloride, a novel antidiabetic compound that improves the general response of target cells to insulin, significantly lowered cholesterol levels in rats fed a hypercholesterolemic diet and produced a significant reduction in cholesterol absorption. Drug treatment was ineffective in rats that were not given dietary cholesterol. To determine whether these effects of pioglitazone hydrochloride might be related to the known ability of this compound to improve the response to circulating insulin, similar studies were conducted in streptozocin-induced diabetic rats with and without insulin replacement. Diabetic rats absorbed a greater percentage of dietary cholesterol than control rats. Treatment of insulin-deficient diabetic rats with pioglitazone alone did not affect cholesterol absorption; however, the combination of insulin and pioglitazone was synergistic to lower absorption of cholesterol and circulating cholesterol and triglycerides. Treatment of either normal rats or diabetic rats receiving insulin with pioglitazone hydrochloride produced a twofold decrease in the ratio of total cholesterol to high-density lipoprotein cholesterol. These results suggest that treatments that improve insulin sensitivity may also have a positive impact on coronary artery disease associated with diabetes.

Steroid binding specificity of the hamster uterine progesterone receptor.

The relative binding affinities (RBA) of 51 steroids were determined for the uterine progesterone receptor of the proestrous hamster. The receptor demonstrated a high specificity for progesterone; most structural modifications to the progesterone molecule resulted in a substantial reduction in binding affinity. Only six steroids had relative binding affinities similar to progesterone (RBA=100): 17 alpha-ethinyl-17 beta-methoxy-4-androsten-3-one (RBA=85); 6 alpha-fluoro-4-pregnene-3,20-dione (RBA=94); 17,21-dimethyl-19-nor-4,9-pregnadiene-3,20-dione (RBA=96); 19-nor-4-pregnene-3,20-dione (RBA=110); 21-fluoro-4-pregnene-3,20-dione (RBA=119); and 17 alpha-ethinyl-17 beta-methoxy-4-estren-3-one (RBA=123).

Peripheral plasma progesterone during egg transport in the rabbit.

Summary Peripheral plasma progester-one concentrations were measured in New Zealand rabbits every 6 hr beginning 12 hr before and continuing until 96 hr after either natural mating, hCG injection, or saline injection. The number of ovulation points in naturally mated animals (9.3 ± 0.6, mean ± SE) was not significantly different from that in hCG-injected animals (8.6 ± 1.5). There was a surge in progesterone secretion following both mating and hCG injection. Plasma progesterone concentrations reached a peak prior to ovulation and then fell to basal levels at the time of ovulation. Beginning at approximately 30 hr after the ovulation-inducing stimulus, there was a progressive, significant (P < 0.001) increase in plasma progesterone concentration, which continued for the duration of the sampling period. The initiation of the postovulatory increase in progesterone secretion corresponds temporally with the movement of eggs from the ampullary-isthmic junction into the isthmus. The progressive increase in plasma progesterone between 30 and 72 hr after the induction of ovulation corresponds with the gradual movement of eggs through the isthmus into the uterus. The data suggest that movement of eggs through the oviductal isthmus is influenced by the postovulatory secretion of progesterone.

Effect of 15(S)-15-Methyl Prostaglandin F2α on Human Oviductal Motility and Ovum Transport*

The effects of an intravenous infusion of 15(S)-15-methyl prostaglandin F2alpha (PGF2alpha) on oviductal motility and ovum transport were studied in women who were scheduled for elective tubal sterilization. Infusion rates of 0.38 microgram/kg/hour or higher caused an increase in oviductal motility in all patients. Lower infusion rates did not always cause a stimulation of motility. Low infusion rates generally caused an increase in the amplitude of contractions without any effect on basal oviductal tone. The higher infusion rates usually caused a large increase in basal tone as well as an increase in the amplitude of contractions. Ova were recovered from the oviducts of five patients who had received an intravenous infusion of 15(S)-15methyl PGF2alpha. The ova were recovered from the ampulla in three patients, from the ampullary-isthmic junction in one patient, and from the isthmus in one patient. Since one would expect to recover ova from the oviducts at similar times under normal circumstances, there was no evidence that this prostaglandin treatment caused an acceleration of ovum transport. These data support the conclusion that a PGF analog which stimulates oviductal motility does not necessarily also accelerate ovum transport in women.

Effect of Vaginally Administered 15[S]15-Methyl-PGF.2αon Egg Transport and Fertility in Rabbits

Summary The effects of vaginal suppositories containing 1.0 mg of 15[S]15-methyl-PGF2α on oviductal motility, egg transport, and fertility were determined in rabbits. Suppository treatment caused a significant increase (P < 0.02) in the amplitude of oviductal contractions, and a decrease in the frequency of contractions (P < 0.04). Altered oviductal motility persisted for an average of 2 hr after treatment. Treatment with 1, 2, or 3 suppositories at various times after ovulation caused a significant reduction in the number of eggs located in the oviducts (P < 0.025). There was, however, a great deal of variation in egg recovery in treated animals (range 0 to 100%). Treatment of mated rabbits during the time of tubal egg transport caused a significant reduction in the number of Day-12 implants (P < 0.05). The percentage of corpora lutea represented by Day-12 implants was similar to egg recovery rates in animals similarly treated. The treatment had no effect on fetal survival from Day 12 to 28 of pregnancy. The decrease in fertility caused by these vaginal suppositories is presumably due to the stimulatory effect on oviductal motility which accelerates tubal transport of the embryos into the uterus. Embryos that arrive in the uterus prematurely probably do not implant and degenerate or are expelled.

Arrest of folliculogenesis and inhibition of ovulation in the monkey following weekly administration of progestins

Studies were undertaken in the rhesus monkey to determine whether development of a dominant ovarian follicle could be repeatedly arrested by the administration of a progestin on day 7 of the menstrual cycle, and then every 7 days thereafter regardless of menstrual bleeding history. Progesterone (7.5 mg), norethisterone (1.5 mg), and 17 alpha-ethinyl-17 beta-methoxy-7 alpha-methyl-4-estren-3-one (1.0 or 1.5 mg) effectively inhibited ovulation when injected intramuscularly once a week for 8 weeks. Orally administered STS 557 (17 alpha-cyanomethyl-17 beta-hydroxy-4,9-estradien-3-one, 1.0 mg) also inhibited ovulation. Two structurally related steroids (17 beta-methoxy-4-estren-3-one, 1.0 mg; and 17 beta-methoxy-7 alpha-methyl-4-estren-3-one, 1.5 mg) did not inhibit ovulation when given intramuscularly at the indicated doses. Although weekly administration of certain progestins effectively arrested follicular development and inhibited ovulation in the primate, the treatment was accompanied by disturbances in menstrual bleeding patterns.

Effects of PGF2α and PGF2α, 1–15 lactone on the corpus luteum and on early pregnancy in the rhesus monkey

The effects of prostaglandin (PG)F2alpha and PGF2alpha, 1-15 lactone were compared in luteal phase, non-pregnant and in early pregnant rhesus monkeys. Animals treated with either PG after pretreatment with human chorionic gonadotropin (hCG) had peripheral plasma progesterone concentrations that were not statistically different from those in animals treated with hCG and vehicle. However, menstrual cycle lengths in monkeys treated with PGF2alpha, 1-15 lactone were significantly (P less than 0.02) shorter than those in vehicle treated animals. In the absence of hCG pretreatment, plasma progesterone concentrations were significantly (P less than 0.008) lower by the second day after the initial treatment with either PGF2alpha or PGF2alpha, 1-15 lactone than in vehicle treated monkeys. Menstrual cycle lengths in monkeys treated with either PG were significantly (P less than 0.04) shorter than those in animals treated with vehicle. There were no changes in plasma progesterone concentrations in early pregnant monkeys treated with PGF2alpha, and pregnancy was not interrupted. In contrast, plasma progesterone declined and pregnancy was terminated in 5 of 6 early pregnant monkeys treated with PGF2alpha, 1-15 lactone. These data indicate that PGF2alpha, 1-15 lactone decreases menstrual cycle lengths in non-pregnant rhesus monkeys. More importantly, PGF2alpha, 1-15 lactone terminates early pregnancy in the monkey at a dose which is less than an ineffective dose of PGF2alpha.

Design criteria for controlled release delivery systems of carboprost methyl

Abstract Permeabilities of carboprost methyl (15(s)-15 methyl prostaglandin F 2 α methyl ester) were determined for a series of synthetic polymeric membranes. Membrane compositions consisted of a polyurethane ether and a series of poly(co-ethylene) vinyl acetate copolymers with vinyl acetate concentrations varying from 9% w/w to 60% w/w. Permeability increased as a function of the percent vinyl acetate in the copolymer. The increase in permeability was mainly due to an increase in the solubility of carboprost methyl in the polymer. Diffusion coefficients were independent of vinyl acetate concentrations above 9% w/w. The highest permeability and solubility value was associated with the polyurethane polymer. Membranes of identical composition yielded different transport rates depending upon the method of preparation (casted versus blown) and transport rates were inversely related to the thickness of the membrane. Permeability was shown to be a key parameter in determining the sequencing of polymeric membranes in the design of laminated controlled release delivery systems for carboprost methyl.

Fluid Retention by the Rabbit Oviduct

Abstract Factors affecting occlusion of the isthmic portion of the oviduct in Dutch-belted rabbits were evaluated by measuring the amount of fluid that accumulated in oviducts that were ligated only at the ovarian end. Very little fluid accumulated in the oviducts of estrous rabbits. Induction of ovulation with human chorionic gonadotropin (hCG) or treatment with Depo-estradiol cypionate (ECP) caused a significant increase in the accumulation of tubal fluid at 48 hr. Indomethacin inhibited fluid retention in ECP-treated rabbits, but had no effect in rabbits injected with hCG. Progesterone antagonized the effect of hCG, but not that of ECP. The effect of progesterone in hCG-treated rabbits could not be attributed to a decrease in fluid secretion rate since the amount of fluid in oviducts that were ligated at both ends was similar in rabbits treated with hCG or hCG plus progesterone. In contrast to the results at 48 hr, indomethacin had no effect on fluid accumulation at 72 hr in ECP-treated rabbits. However, indomethacin did reduce the amount of fluid that accumulated in the oviducts of rabbits injected with both hCG and ECP. Prostaglandin (PG) E1, PGE2, and PGF2α had no effect on fluid retention. These data indicate that an interaction exists between the occlusive effects of hCG and ECP. At 48 hr the effect of hCG seems not to be mediated by PGs, but the effect of ECP is PG related. However, at 72 hr the effect of ECP cannot be blocked by inhibiting PG synthesis, but the occlusive effect of hCG plus ECP may be mediated by PGs.