The influence of age on bone mineral regulating hormones.

The objective of this study was to determine the effect of age on the blood levels of 1,25-dihydroxyvitamin D (1,25(OH)2D) and immunoreactive parathyroid hormone (iPTH) in normal, healthy males and females. A total of 855 normal subjects (361 males and 494 females) were studied. The results show that for healthy males, blood concentrations of 1,25(OH)2D remained essentially constant with increasing age up to age 65, and then the concentrations decreased significantly. For healthy females, 1,25(OH)2D increased up to age 65, and then decreased at a significant rate. Serum iPTH in males increased with advancing age, but the rate of increase was greater after age 65. In females a significant increase in iPTH concentrations did not occur until after age 65. Serum creatinine increased in both males and females with advancing age.

Prostaglandins: perspective in obstetrics and gynecology.

PIP: Prostaglandins (PGs) are metabolic regulators produced at the cellular level to exert a local action, usually of a modulating type. Their biological function is analogous to cycle adenosine 3",5' monophosphate (cAMP) (i.e., acting as messengers) rather than to a steroid function, although PGs interact with both cAMP and steroids. Clinicians need to know the endogenous biosynthesis of PGs, their metabolism, and their detection to use PGs therapeutically with competence. Apparently, endogenous biosynthesis of PGs is catalyzed by a microsomal enzyme system composed of many different enzyme types. The required precursors are essential fatty acids, arachidonic acid, and bis-homo-y-linolieic acid in the unesterified form. Molecular oxygen and other cofactors are also required. This biosynthesis was worked out in sheep seminal vesicles, but it is now recognized that virtually all tissue types in mammals synthesize PGs. The metabolic degradation and inactivation of PGEs and PGFs, both derived from the same intermediate, are extremely rapid (Samuelsson et al., 1971, 1972). The most important first step is oxidation of the 15-hydroxyl group to a carbonyl, which modifies the activities of PGs and allows further degradation and elimination via urine; this series of steps protects the body from these potent agents. Detection and analysis are best achieved by deuterium-labeled intermediates which are determined by mass spectrometry. It is important to remember that various tissues have widely varying responses to PGs; for example, PGs have luteolytic action in sheep but do not induce uterine contractions, whereas the opposite seems true in humans.^ieng

Developing applications of prostaglandins in obstetrics and gynecology.

PIP: Clinical research has shown that prostaglandins (PGs) play an important role in every phase of human reproduction. The logical consequence of early basic biological research into PGs is the current interest in clinical evaluation of PGs as agents to induce labor and abortion and to stimulate menstruation. This is a review of the current literature dealing with PG research. Both PGF2alpha and PGE2 are known to induce labor at term when administered by intravenous infusion. Their relative effectiveness as compared to oxytocin has yet to be assessed. Intravenous infusion of PGE1, PGE2, and PGF2alpha will also induce abortion. Current research is being directed toward finding more practical methods of administration than continuous intravenous infusion. There is hope that PGs will be able to be used as a once a month contraceptive administered at the time of expected menstruation following exposure and a possible unwanted pregnancy. The exact mechanism of action of PGs on smooth muscle is still largely unknown. The differences in response of a specific muscle to different PGs have also not received much research attention. Little is known, for example, regarding the action of PGs on the cervix as opposed to the rest of the uterus. Particularly unknown is the mechanism of action of PGs at the molecular level. In most of the situations studied, PGs seem to stimulate adenyl cyclase activity and cyclic adenosine monophosphate formation or accumulation.^ieng