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Previous studies, including our own, have demonstrated that muscle sympathetic nerve activity (MSNA) is increased in patients with essential hypertension compared with normotensive subjects. However, the features of sympathetic nerve activity are still unknown in secondary hypertension. We examined MSNA in eight patients with renovascular hypertension and in 11 patients with primary aldosteronism. Twenty patients with essential hypertension and 20 normotensive subjects who were age-matched to the patients with renovascular hypertension and those with primary aldosteronism were also studied. The MSNA of a bundle of the tibial nerve was recorded by microneurography in supine subjects and expressed as both burst rate (bursts/min) and burst incidence (bursts/100 heart beats). Plasma renin activity and the plasma concentration of angiotensin II and aldosterone were also measured. MSNA was increased in the patients with renovascular hypertension compared with the patients with primary aldosteronism and those with essential hypertension and the normotensive subjects (p<0.01 for each). MSNA was decreased in the patients with primary aldosteronism compared with those with essential hypertension (p<0.01), and it was smaller than in the normotensive subjects (p<0.l). Furthermore, MSNA, plasma renin activity, and the plasma concentration of angiotensin II decreased significantly in five patients with renovascular hypertension 4-10 days after successful percutaneous renal angioplasty. Thus, the changes in MSNA seem to characterize the patbophysiology of renovascular hypertension and primary aldosteronism. Activation of the renin-angiotensin system may be involved in the increase in the central outflow of sympathetic nerve activity, thus exacerbating hypertension in patients with renovascular hypertension. (Hypertension 1991;17:1057-1062) N eurogenic mechanisms have often been implicated in the pathogenesis of hypertension. Although the plasma concentration of norepinephrine has been used as a rough index of overall sympathetic nerve activity, its pathophysiological implications need careful evaluation since the plasma concentration of norepinephrine is determined by many factors, such as the reuptake and metabolic degradation of norepinephrine and its spillover from the nerve endings.1 ' 2 Accordingly, we have investigated sympathetic tone by directly recording the muscle sympathetic nerve activity (MSNA) contained in a bundle of the tibial nerve using a microneurographic technique in the conscious human.3 -8 Our previous studies have demonstrated that the baroreflex control of sympathetic

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To investigate the pathophysiological role of the sympathetic nervous system in essential hypertension, this study recorded the muscle sympathetic nerve activity (MSNA) of the tibial nerve and examined the age-related changes in patients with essential hypertension and in normotensive persons. There were 43 normotensive subjects (16-69 years old) and 63 patients with essential hypertension (18-67 years old) in the study. The MSNA at rest, recorded by microneurography, was evaluated by burst rate (bursts/min), burst incidence (bursts/100 heart beats), and spike frequency (spikes/min). The MSNA recording showed a high reproducibility with a correlation coefficient of 0.86 (p<0.0l) in repeated studies. The MSNA was significantly greater in the hypertensive patients than in the normotensive subjects, irrespective of activity units (p<0.0l), and this finding was consistent in the young (30 years old or less), middle-aged (31-50 years old), and old groups (51 years old or more). Furthermore, MSNA showed a significant positive correlation with age both in the normotensive subjects (r=0.43, p<0.01 for burst rate; r=0.49, /?<0.01 for burst incidence; and r=0.50, p<0.01 for spike frequency) and in the hypertensive patients (r=0.40,/><0.01 for burst rate; r=0.44,p<0.01 for burst incidence; and r=0.40, /><0.01 for spike frequency). Although there was a significant positive correlation between plasma norepinephrine concentration and MSNA in the hypertensive patients and the normotensive subjects, the difference in plasma norepinephrine concentration between the two groups was not significant at any age level. These results indicate that sympathetic nerve activity is increased in patients with essential hypertension at any age level and plays a long-term role in the development and maintenance of blood pressure elevation. (Hypertension 1989; 13:870-877)

A theoretical equation of the reversible polarographic current-potential curves for the ion transfer across the aqueous/organic interface facilitated by the neutral macrocyclic ligand present in the o-phase is derived without any limitation on the magnitude of distribution constant of the ligand. In two limiting cases, which have been employed in common experimental practice, i.e., (A) the bulk concentration of cation, c*M, in the aqueous phase &gt;&gt; that of ligand, c*L, in the organic phase and (B) the reverse condition, c*M&lt;&lt;c*L, the equation of current-potential curves becomes the same in form as that of reversible D. C. polarographic waves. It is shown that the limiting current is controlled by diffusion of ligand in the organic phase for (A) and of cation in the aqueous phase for (B) and, on the other hand, the half-wave potential depends on c*M for (A) and on c*L for (B). Furthermore, an analysis method to determine the complex formation constants in the organic phase (and in the aqueous phase for favorable cases) from the concentration dependence of the half-wave potential is presented. The theoretical predictions are verified experimentally using dibenzo-18-crown-6 and 18-crown-6 as macrocyclic ligands and sodium, cesium, barium, and oxonium ions as transferred cations.