Renin (Special Request Assay)

Renin is released by the juxtaglomerular apparatus of the kidney in response to a decrease in arterial blood pressure (including decreased blood volume) or a reduced Na content of glomerular ultrafiltrate. It is the first part in the Renin-Angiotensin-Aldosterone-System.

Renin activates Angiotensin by cleaving Angiotensinogen to release Angiotensin I which through the action of Angiotensin converting enzyme (ACE) produces Angiotensin II. In turn, Angiotensin II, stimulates the release of aldosterone from the adrenal cortex. The action of aldosterone should promote the resorption and retention of Na and restore blood volume.

The measurement of Renin can be particularly useful in the investigation of hypokalaemia and hypertension.

In conditions where there is an elevated aldosterone, it is helpful to discover if that is “appropriate”, and is the result of Renin activation or “inappropriate”, and likely to be autonomous such as functional adrenal cortex neoplasia (aldosteronoma).

The measurement of Renin is therefore essential in the investigation of hypertension or situations of elevated aldosterone.

We now offer a full Hypotension/Hypokalaemia profile comprising Plasma RENIN, Aldosterone and Na/K ratio including the calculation of Aldo/Renin ratio.

Sample preparation for the assay of plasma Renin

Blood must be collected into pre-chilled tubes containing EDTA as an anticoagulant.

HEPARIN must not be used as this interferes with the assay.

The samples must be kept cold and ideally centrifuged in a refrigerated centrifuge to separate the plasma. The plasma samples must then be aliquoted and frozen at less than – 10°C until assayed.

Samples must be sent to the laboratory frozen and courier is essential.

Haemolysed or lipaemic samples must not be used in the assay so great care is needed when blood sampling to ensure samples do not become haemolysed.

At least 1.0 mL of EDTA plasma MUST be sent for the analysis of Renin otherwise it may not be possible to get a valid result.