Deficient noradrenergic response to oral glucose in hypertensives

The blood pressures of hypertensives lower more following a meal than those of normotensives; the reason for this difference is not known. We gave an oral glucose tolerance test to 33 normotensives and 16 hypertensives matched for age, sex, race, height, and weight. The hypertensives had slightly higher glucose levels and similar insulin levels. The diastolic blood pressures of hypertensives decreased by approximately 10 mmHg, more than twice as much as those of normotensives, but their heart rates did not change. Glucose increased the normotensives' heart rates by approximately 5 beats/min. The hypertensives' plasma norepinephrine responses to a glucose meal were less than one-half of normal. These findings suggest that hypertensives have a large drop in blood pressure following glucose because of a deficient sympathetic nervous response to eating. This may reflect both impaired baroreflexes and deficient insulin-mediated stimulation of the sympathetic nervous system.