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Similar observations have been made in normotensive humans after intravenous PGA administration. PGA has little positive or negative chronotropic or inotropic effect on the isolated perfused heart, indicating that its hypotensive effects are peripherally mediated. During PGA, or PGA, administration, there is a redistribution of renal blood flow from medulla to cortex, with an associated rise in total blood flow, natriuresis, kaliuresis, and diuresis, leading to a reduction in plasma volume. However, the natriuresis with PGA's may be due not only to changes in blood flow but also to metabolic inhibition of NA-KATPase (Table 3), which results in a decrease in active sodium reabsorption. Antihypertensive Effects in Hypertensive Humans
The first prostaglandin administered to a hypertensive human being was PGA,, isolated from the kidney as medullin (3). Blood pressure fell from hypertensive to normotensive levels as a result of peripheral arteriolar dilatation, and there was a reflex increase in heart rate and cardiac output. In a series of 20 hypertensive patients, PGA, produced similar effects (5, 6). Its administration to the human being differed most notably from its administration to normotensive animals in that the lowering of blood pressure from hypertensive to normotensive levels in the human being is not transitory but lasts as long as the compound is infused. Reproductive System
Prostaglandins of the E and F(but not A) classes have marked effects on the reproductive system of nonprimates and primates, including the human. Their main actions are (1) to stimulate gravid uterine muscle to contract, (2) to produce luteolysis and decreased progesterone secretion, and (3) to act at the pituitary-hypothalamic levels as mediators of luteinizing hormone releasing factor (LRF)on luteinizing hormones (LH) secretion. Most of these actions involve stimulation of adneyl cyclase activity, leading to a rise in intracellular C-AMP.
Abortion
The most immediate clinical application of prostaglandins appears to be in mid-trimester abortion by intra-amniotic injection. Suction curettage still remains preferable to prostaglandin administration during the first trimester. Although prostaglandins have been suggested as effective
Tot 4511 Sus – FGHFCT, 2006
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