Biomedical subjects

J Sowers

Publications and source records attributed to J Sowers.

25 records · Page 2Linked to original sources

PubMed1983

Effect of aldosterone on the human erythrocyte sodium--potassium pump in vitro.

1. The effects of aldosterone in vitro on the Na+, K+-dependent ATPase activity of isolated human erythrocyte membranes and on rubidium (86Rb) uptake and [3H]ouabain binding of intact erythrocytes were studied. 2. ATPase activity was nearly doubled (0.061 +/- 0.006 to 0.110 +/- 0.01 mumol of Pi h-1 mg-1 of protein) by the addition of a physiological concentration of aldosterone (2.7 X 10(-10) mol/l). Higher concentrations had no greater effect. 3. Aldosterone had no significant effect on 86Rb uptake or [3H]ouabain binding. 4. Erythrocytes contain aldosterone at concentrations similar to that in plasma. The effect of aldosterone on ATPase is probably maximal.

Adult↗

PubMed1982

Domperidone elevates rat plasma beta-endorphin-immunoreactivity when administered peripherally but not intracerebroventricularly.

Domperidone, a dopamine receptor antagonist which apparently does not penetrate the blood-brain barrier in rats was administered to adult males. Domperidone 500 micrograms and 100 micrograms, given through intracarotid cannula, significantly elevated plasma beta-endorphin-immunoreactivity (beta-EP-I) at +15 min. To show that only a peripheral site(s) of action is implicated, domperidone was given to rats by cannulae implanted into both lateral ventricles. Plasma beta-EP-I was unaffected by this route of administration. These results suggest that plasma beta-EP-I is tonically inhibited by dopamine acting at site(s) outside of the blood-brain barrier.

Animals↗

PubMed1982

Sleep related breathing disorders in older men: a search for underlying mechanisms.

The incidence of sleep-related breathing disorders (SRBDs) associated with hemoglobin desaturation was determined by nocturnal polygraphic evaluations in 26 healthy men, aged 55-70 years. Sixteen subjects (62%) had abnormal rates of at least 12 episodes per hour of sleep: 8 had occlusive, and 8 had central apnea or hypopnea. During waking ten of 16 SRBD subjects and only one subject without SRBDs exhibited either an elevated nasopharyngeal airway resistance (n = 4) or a reduced ventilatory response to hypercapnia (n = 4) and/or hypoxia (n = 3). However, these abnormalities were not related to the type or severity of SRBDs, and 6 subjects with SRBDs demonstrated no respiratory defect. We conclude that SRBDs have a very high incidence in older males and are not usually secondary to pulmonary cardiac, neurological, or behavioral disorders. Additionally, we hypothesize that abnormalities in ventilatory control or upper airway resistance contribute to SRBDs, but depression of brain stem reticular formation activity during sleep plays a primary role in these disorders. Factors related to both aging and SRBDs are reviewed. These include reduced chemoreceptor responses, altered steroid hormone metabolism, and use and metabolism of hypnotic drugs and alcohol.

Aged↗

PubMed1982

Dopamine regulates canine plasma beta-endorphin-immunoreactivity levels.

Intravenous administration of the dopamine antagonists domperidone and metoclopramide elevates canine plasma beta-endorphin immunoreactivity. Pretreatment with dopamine, but not dexamethasone, inhibits this effect. Sephadex G-50 chromatography shows that this response is due to beta-endorphin-like peptides, not beta-lipotropin. These findings indicate that pituitary beta-endorphin secretion is tonically inhibited by dopamine and suggest that the intermediate lobe is the source of this secretion.

Animals↗

PubMed1982

Effects of bromocriptine on renin, aldosterone, and prolactin responses to posture and metoclopramide in idiopathic edema: possible therapeutic approach.

This study examines the effect of bromocriptine therapy (2.5 mg three times daily for 4-5 days) on orthostatic increases in weight, PRA, plasma aldosterone, and PRL in patients with idiopathic edema and in normal female controls. Additionally, PRA, aldosterone, and PRL responses to the dopamine antagonist metoclopramide were examined in both groups before and after bromocriptine. Edema patients demonstrated greater orthostatic weight gain and greater aldosterone and PRL responses to upright posture and isometric handgrip exercise. However, after bromocriptine treatment, these orthostatic responses were similar to those noted in normal controls. After metoclopramide administration, edema patients displayed normal PRA and aldosterone responses, but had exaggerated PRL responses. After bromocriptine, the PRL, but not the PRA or aldosterone, response to metoclopramide was greatly reduced. The PRL responses to metoclopramide were similar in edema patients and controls after bromocriptine treatment. These data suggest that there is decreased dopaminergic inhibition of aldosterone and PRL in response to upright posture in the idiopathic edema syndrome. Diminished orthostatic urinary excretion of sodium appears to be related to decreased dopaminergic tone in this syndrome. These abnormalities are largely corrected by tolerable doses of the dopamine agonist bromocriptine.

Adult↗

PubMed1981

The effect of weight reduction on blood pressure, plasma renin activity, and plasma aldosterone levels in obese patients.

We investigated the relation between changes in the renin-aldosterone axis and reduction in blood pressure in 25 obese patients placed on a 12-week reducing diet; sodium intake was either medium (120 mmol) or low (40 mmol). Plasma renin activity (PRA) declined with weight loss, so that by 12 weeks there was a significant decrease in PRA (P less than 0.01) as well as plasma aldosterone (P less than 0.05), regardless of sodium intake. Weight loss with low sodium intake was equal to that with medium intake. The reduction in PRA but not in aldosterone correlated with weight loss in both sodium-intake groups (r = 0.58). Mean arterial pressure fell significantly and equally in both groups, correlating with weight loss throughout the study (r = 0.56) and with PRA from the fourth through 12th weeks (r = 0.48) These results demonstrate that weight loss is accompanied by reductions in PRA and aldosterone; PRA reductions, irrespective of sodium intake, may contribute to the decline in blood pressure.

Adult↗

PubMed1981

Plasma aldosterone and corticosterone responses to adrenocorticotropin, angiotensin, potassium, and stress in spontaneously hypertensive rats.

The responses of plasma aldosterone and corticosterone to ACTH, angiotensin II (AII), and potassium chloride (KCl) infusion and the aldosterone, corticosterone and PRA responses to immobilization stress were studied in 2-month-old spontaneously hypertensive rats (SHR) and age-matched Wistar-Kyoto (WKY) normotensive controls. Basal levels of plasma aldosterone and corticosterone were greater and PRA was less in the SHR than in the WKY. Aldosterone and corticosterone responses to graded AII were similar in both groups. Aldosterone and corticosterone responses to graded doses of KCl and ACTH, however, were significantly greater in SHR than in WKY normotensive rats. Plasma corticosterone, PRA, and aldosterone responses to immobilization stress were reduced in SHR compared to WKY. At 2 months of age, blood pressure was definitely elevated in SHR and was associated with low PRA and relatively high basal levels of aldosterone and corticosterone. Discordance between the renin-angiotensin system and mineralocorticoid secretion in the SHR may be due to enhanced adrenal sensitivity to factors such as ACTH and potassium. Suppressed PRA in SHR may be due, in part, to increased mineralocorticoid secretion, resulting in sodium retention and intravascular volume expansion.

Adrenocorticotropic Hormone↗