Effects of oral salt loading on beta-adrenergic receptor responsiveness in normal and hypertensive subjects.
The effect of oral salt loading (400 mmol per day of NaCl for 7 days) on cardiac and pancreatic beta-receptor responsiveness has been evaluated in 12 patients with established essential hypertension and in seven age-matched control subjects. Cardiac beta-receptor responsiveness was evaluated by assessing the dose of isoprenaline which increased a stable heart rate by 25% (chronotropic dose 25%, CD 25%). Pancreatic beta-receptor responsiveness was measured by the incremental areas of insulin secretion induced by iv infusion of increasing amounts of isoprenaline. Before salt load, CD 25% was significantly higher in hypertensives compared with controls (7.84 +/- 1.34 micrograms vs 3.9 +/- 0.48 micrograms, P less than 0.05) while there was no difference in the isoprenaline-induced insulin secretion between the two groups of subjects. After salt loading, CD 25% was significantly reduced in hypertensive patients but was not modified in normal subjects. Therefore, the difference in CD 25% was no longer detectable between the two groups (5.5 +/- 1.42 micrograms vs 3.2 +/- 0.48 micrograms in normal subjects and in hypertensives, respectively, NS). Furthermore, salt loading failed to induce any change in isoprenaline-induced insulin secretion in either groups. These results support the existence of a relationship between sodium intake and adrenergic beta-receptor responsiveness in human hypertension.
D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D001794:Blood Pressure / Q000187:drug effects; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006973:Hypertension / Q000378:metabolism* / Q000503:physiopathology; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism; D007545:Isoproterenol; D008297:Male; D008875:Middle Aged; D009206:Myocardium / Q000378:metabolism; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*; D012965:Sodium Chloride / Q000494:pharmacology*; D013268:Stimulation, Chemical
D001786:Blood Glucose; D007328:Insulin; D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D012965:Sodium Chloride; D007545:Isoproterenol