ERYTHROCYTE NA-H+ EXCHANGE ACTIVITY IN ESSENTIAL HYPERTENSIVE AND OBESE PATIENTS - ROLE OF EXCESS BODY-WEIGHT()

Introduction: Several authors have described increased Na+-H+ exchange r activity in essential hypertension, and an increase in activity of t his transport system has also been postulated in situations of hyperin sulinism, such as obesity and essential hypertension. Methods: We meas ured Na+-H+ exchanger activity in a group of 37 subjects with essentia l hypertension (18 obese, 19 non-obese), in a group of nine normotensi ve obese subjects and in a control group of 16 healthy volunteers. Pla sma insulin and glucose values during an oral glucose tolerance test w ere evaluated, together with other variables such as plasma aldosteron e, plasma renin activity and plasma potassium. Results: Na+-H+ exchang er system activity did not appear to be abnormally raised in the hyper tensive subjects, but was significantly increased in the normotensive obese group. Upon dividing the hypertensive subjects into two subgroup s on the basis of body mass index, it was noted that, whereas the non- obese hypertensives showed Na+-H+ exchanger activity patterns similar to those in controls, the obese hypertensive subjects exhibited increa sed activity of the transport system. Na+-H+ activity correlates with body mass index and shows a significant inverse correlation with plasm a potassium. No correlations were found between Na+-H+ exchanger activ ity and the sum of plasma insulin values during the oral glucose toler ance test. Conclusion: Na+-H+ exchanger overactivity appears to be cha racteristic in overweight subjects, but would not appear to be a speci fic feature of essential hypertension. The increased Na+-H+ exchanger activity observed in obese subjects may be postulated to be related to the hypermineralocorticoidism characteristic of this condition.