Renal high-molecular-weight renin: unusual formation in the aged stroke-prone spontaneously hypertensive rats

A high-molecular-weight renin (HMWR) was detected in the plasma (molecular weight 50,600) and renal cortical homogenate (molecular weight 57,000) of 25-week-old male stroke-prone spontaneously hypertensive rats (SHRSP), in contrast to the renin with a molecular weight of 38,000 in normotensive Wistar Kyoto rats (WKY) and 5-week-old SHRSP. However, renin granules contained only the renin with a molecular weight of 38,000, indicating that the renal HMWR is not a native form but is probably a renin/renin-binding protein complex. Such HMWR was not produced when the renal cortex was homogenized with an equal amount of renal cortex of WKY. Further, the HMWR of the aged SHRSP was converted into the 38,000-dalton renin, when incubated with the extract of renal cortex of WKY. Thus, the existence of a renal cortical substance that converts the renal HMWR into the 38,000-dalton renin was evidenced. This substance was fractionated with DEAE-cellulose and was characterized as a putative SH enzyme. We conclude that a deficiency in the HMWR-converting substance may be attributed to the unusual formation of HMWR in the aged SHRSP.