Assay of human erythrocyte sodium‐dependent lithium efflux: the importance of timing of blood sampling

Abstract

Abstract. The activity of the human erythrocyte sodium-lithium countertransport (SLC) is stable over long periods in individuals. However, it is becoming increasingly evident that the transport system is susceptible to modulation, both acutely and chronically, by various factors. In this study, the authors observed temporal variation in SLC over a period of 10 h (08.00-18.00 hours) in healthy volunteers. was lower than at 'midday' (P < 0 . 045) but higher than in the morning (P < 0 . 037). These changes were not accompanied by any significant change in the affinity of the transporter for external sodium, K m . Changes in SLC V max did not correlate with the corresponding ones in either plasma cortisol or aldosterone. However, they correlated well with those in plasma renin activity, the correlation between mid-day and a.m. sets of values (r 0 . 718; P 0 . 019) being better than that between mid-day and p.m. (r 0 . 688; P 0 . 028). The authors conclude that changes in SLC occur during the day, and this need be taken into account in the planning and execution of studies involving determination of the activity of this transport system.

Effects of oral contraceptives containing different progestogens on sodium-lithium countertransport in normal females

“…17 There are reports that increased plasma renin activity, resulting from increased level of the hormone, is associated with increased SLC activity. 18,19 Given the well recognised capacity of oestrogen-progesterone combinations to induce increase in plasma renin activity, 20 it could be argued that the latter is a possible mechanism for the increase in SLC activity observed in those on ethinyloestradiol/desogestrel combination in the present study. However, such argument is flawed by the fact that the oestrogen-progesterone combination-induced increase in plasma renin activity is due more to an increase in plasma level of renin substrate than that of the hormone renin itself.…”

Relevance of erythrocyte Na+/Li+ countertransport measurement in essential hypertension, hyperlipidaemia and diabetic nephropathy: a critical review

“…Other factors that have been investigated for their effect on Na þ /Li þ CT activity in relation to hypertension are alcohol consumption [28,39,40], renin and aldosterone blood concentrations [41,42] and use of oral contraceptives [28]. These studies, however, represent contradictory findings and/or need confirmation.…”