UC San Diego

Hypertension is associated with elevated risk for cardiovascular diseases and renal failure. Recent evidence suggests that there exist elevated levels of unchecked degrading enzymatic activity in hypertensives that are not normally present in healthy controls. These uncontrolled enzymes have been shown to cleave receptors, leading to the destruction of membrane receptors and impair cellular and bodily functions. The objective of this study is to examine the possibility of plasma protein degradation by the enhanced enzymatic activity in hypertension. Blood and plasma proteinase levels and activity were determined and compared in the control Wistar Kyoto rat and the spontaneously hypertensive rat (SHR). Plasma proteins were analyzed for degradation, and peptide fragment levels were compared between the WKY and SHR group. A candidate protein, albumin, was examined for evidence of fragmentation in the plasma and urine. Kinetic spectrometric analysis results showed that the SHR has elevated proteinase activity (p < 0.05) in both the plasma and whole blood. Gelatin gel zymography showed elevated levels of ̃19.1 kDa, 67.3 kDa and 73.7 kDa gelatinase (possibly MMP7, MMP2, pro-MMP2, respectively) in the plasma of the SHR (p < 0.05). The SHR plasma was found to have reduced ̃ 21.9 kDa, 33.3 kDa, 46.2 kDa and 226.1 kDa protein levels, increased ̃2 kDa protein/peptide level and elevated plasma protein fragment levels (p < 0.05). A low molecular weight protein/peptide (̃17.2 kDa) was elevated in the SHR urine. Albumin fragments (̃17 kDa) were discovered in increased levels in the SHR urine (p < 0.05). Plasma incubation studies showed elevated fragment formation rate in the SHR plasma (p < 0.05) and the formation rate seems to be lowered by the addition of 10 mM EDTA. These results provide for the first time a kinetic characterization of the enhanced proteinase activity in the SHR plasma. The evidence suggests that the enhanced enzymatic level in the circulation of the SHR can cause not only receptor cleavage, but also plasma protein degradation, leading to elevated levels of fragment levels in the blood and urine