Aldosterone and in vivo Mineralocorticoid Activity in Normotensive and Hypertensive Man

Initially the measurement of rectal electrical potential difference (PD) appeared to provide the first useful in vivo assay for mineralocorticoid activity in human subjects, since it was shown that the rectal mucosa responds consistently to aldosterone and other mineralocorticoids with a rise of trans mucosal PD (Edmonds & Richards 1970, Edmonds & Godfrey 1970). However, it has been found subsequently that there is a poor correlation between plasma and urinary aldosterone and rectal PD (Nicholls et al. 1975, Beevers et al. 1975, Skrabal 1976), the transmucosal PD being also influenced by other factors including the autonomic nervous system (Lennane et al. 1975). I reported at the meeting of the Royal Society of Medicine's Section of Endocrinology, on 26 October 1977,that the subtraction of the transmucosal PD of a steroid unresponsive mucosa (oral mucosa) from rectal PD eliminates the steroid independent biological variation of rectal PD. 'Subtraction PD' therefore provides a good index of mineralocorticoid activity in normal subjects and patients with adrenocortical insufficiency and hyperaldosteronism. Some of this work has been published meanwhile (Skrabal et al. 1978). This paper is a further analysis of the data already published and includes additional studies in 81 patients with essential hypertension, in 20 patients with primary or secondary hyperaldosteronism and in 13 patients with adrenocortical insufficiency.