Effect of PGD2, PGE2 PGF2 alpha and PGI on blood pressure, heart rate and plasma catecholamine responses to spinal cord stimulation in the rat.
ABSTRACT The following experiments were designed in order to examine the inter-relationships of various prostaglandins (PG's) and the adrenergic nervous system, in conjunction with blood pressure and heart rate responses, in vivo. Stimulation of the entire spinal cord (50v, 0.3-3 Hz, 1.0 msec) of the pithed rat increased blood pressure, heart rate and plasma epinephrine (EPI) and norepinephrine (NE) concentration (radioenzymatic-thin layer chromatographic assay). Infusion of PGE2 (10-30 microgram/kg. min, i.v.) suppressed blood pressure and heart rate responses to spinal cord stimulation while plasma EPI (but not NE) was augmented over levels found in control animals. PGI2 (0.03-3.0 microgram/kg. min, i.v.) suppressed the blood pressure response to spinal cord stimulation without any effect on heart rate or the plasma catecholamine levels, PGE2 and PGF2 alpha (10-30 microgram/kg. min, i.v.) did not change the blood pressure, heart rate or plasma EPI and Ne responses to the spinal cord stimulation although PGF2 alpha disclosed an overall vasopressor effect during the pre-stimulation period. At the pre-stimulation period it was also observed that PGE2, PGF2 alpha and PGI2, had a positive chronotropic effect on the heart rate, the cardiac accelerating effect of PGE2 was not abolished by propranolol. These in vivo studies suggest that in the rat, PGE2 and PGI2 modulate sympathetic responses, primarily by interaction with the post-synaptic elements - PGE2 on both blood vessels and the heart and PGI2 by acting principally on blood vessels.
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ABSTRACT: We have previously shown that plasma membranes from adrenal medulla possess specific high-affinity binding sites for prostaglandins (PGs) E1 and E2. We have now investigated the binding of PGE2 to intact bovine adrenal chromaffin cells and the effects of prostaglandins on the release of catecholamines from these cells. Adrenal chromaffin cells specifically bound PGE2 with a dissociation constant of 2 nM and a concentration of about 40,000 binding sites per cell. Low concentrations of PGE2 inhibited the nicotine-stimulated release of catecholamines from these cells. The effect of PGE2 was biphasic, the maximal inhibitory effect being observed at a concentration of between 1 and 10 nM. Higher concentrations (1 microM) of PGE2 had minimal inhibitory effects on nicotine-evoked noradrenaline release, but instead had a direct stimulatory effect in the absence of cholinergic agonists. Although the stimulatory effects of high concentrations of PGE2 were reproducibly observed in all cell preparations, only about one-half of the cultures tested responded to the inhibitory effects of this prostaglandin. It is possible that PGE2 plays a modulatory role in the regulation of catecholamine secretion from the adrenal medulla.Biochimica et Biophysica Acta 04/1989; 1010(3):369-76. · 4.66 Impact Factor
- Clinical and Experimental Hypertension 01/1982; · 1.46 Impact Factor
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ABSTRACT: We have shown that obese Zucker rats with orthopedic trauma (OZT) exhibit a loss of arteriolar tone in skeletal muscle. We hypothesize that the loss of arteriolar tone in OZT blunts vasoconstrictor responses to hemorrhage, resulting in an impaired blood pressure recovery. Orthopedic trauma was induced with soft tissue injury and local injection of bone components in both hindlimbs in lean (LZT) and OZT (11-13 wk). One day after the orthopedic trauma, blood pressure responses following hemorrhage were measured in conscious control lean, control obese, LZT, and OZT. In another set of experiments, the spinotrapezius muscle of control and trauma animals was prepared for microcirculatory observation. Arteriolar responses to phenylephrine (PE) or hemorrhage were determined. Hemorrhage resulted in similar blood pressure responses in control animals and LZT, but the blood pressure recovery following hemorrhage was blunted in the OZT. In the spinotrapezius, OZT exhibited decreased arteriolar tone and blunted vasoconstrictor responses to PE and hemorrhage. Treatment with glibenclamide improved the blood pressure recovery in the conscious OZT and improved the arteriolar tone, and PE induced vasoconstriction in the spinotrapezius of the OZT. Thus, ATP-dependent K(+) channel-mediated loss of arteriolar tone in OZT blunts the arteriolar constriction to hemorrhage, resulting in impaired blood pressure recovery.AJP Heart and Circulatory Physiology 01/2012; 302(1):H340-8. · 4.01 Impact Factor