Abstract
Blood collection for assay of renin has been re-examined in order to simplify the routine sampling procedure. Our results show that blood taken with either ethylehediaminetetra-acetate(EDTA) or heparin 15U/mlcan be kept for at least 4 h at room temperature without influence on subsequent assay of renin activity by radioimmunoassay of angiotensin I. With more prolonged delay at ambient temperature, samples collected with EDTA show a progressive increase in preincubation angiotensin I blank; correction of the final value by subtraction of this blank gives a spuriously low result. In contrast, samples taken with heparin do not show an increasing blank; collection with heparin is therefore preferable when samples must remain at ambient temperature. However, the final plasma heparin concentration must be kept below 40 U/ml, because higher concentrations inhibit angiotensin I formation. Collection with heparin will simplify sample transport to specialized laboratories.