Biomedical subjects

K F Hilgers

Publications and source records attributed to K F Hilgers.

57 records · Page 4Linked to original sources

PubMed1991

Local angiotensin formation in hindlimbs of uremic hypertensive and renovascular hypertensive rats.

To examine and characterize the vascular renin--angiotensin system in low-renin models of renal hypertension with and without the presence of overt renal insufficiency, we studied the formation and metabolism of angiotensin in isolated perfused rat hindquarter preparations. Rats with 5/6 nephrectomy (5/6NX) and rats with one-kidney, one clip (1K1C) hypertension were compared to sham operated (sham) animals. Angiotensin peptides in plasma or perfusate were characterized by high-performance liquid chromatography and radioimmunoassay (RIA). Plasma angiotensin II was lower, and blood pressure was higher in both experimental groups, compared to sham animals. Plasma angiotensinogen, measured by both direct and indirect RIA, was increased in both experimental groups. The spontaneous release of angiotensin I and angiotensin II from perfused hindquarters did not differ between the groups. Angiotensin I conversion was not different in 5/6NX or 1K1C groups compared with controls. Furthermore, angiotensin conversion was completely inhibited by captopril (1 mumol/l) in all groups. Renin-induced angiotensin release was significantly increased in 5/6NX as compared with sham rats, whereas there was no difference in renin-induced angiotensin release between 1K1C and sham animals. Angiotensin II degradation was significantly attenuated in 5/6NX rats when compared with sham rats (27.6% versus 53.9%, respectively, P less than 0.05) but was unaltered in 1K1C rats. Thus, in chronic uremic hypertension, renin-induced angiotensin formation was increased in the face of decreased angiotensin II degradation. These data suggest that vascular angiotensin may contribute to the elevated blood pressure observed in chronic renal failure. In 1K1C rats, vascular angiotensin formation and metabolism was unchanged despite suppressed plasma angiotensin II.

Angiotensin II↗

PubMed1989

Angiotensin formation in the isolated rat hindlimb.

Local vascular generation of angiotensin was investigated in isolated perfused rat hindquarters. Extraction and combined high-performance liquid chromatography (HPLC)/radioimmunoassay analysis of hindlimb perfusate showed a spontaneous release of angiotensin I (Ang I; 5.0 +/- 3.4 fmol/h) and angiotensin II (Ang II; 31.8 +/- 7.9 fmol/h). Angiotensin converting enzyme (ACE) inhibition with captopril abolished Ang II release while Ang I levels increased more than 10-fold. Perfusion with purified hog renin caused a dose-dependent angiotensin release and vasoconstriction. The renin inhibitor H-142 abolished all effects of renin whereas ACE inhibition prevented Ang II formation and vasoconstriction but increased Ang I levels. Metabolism and pressor effects of synthetic tetradecapeptide renin substrate (TDP), Ang I and Ang II were studied using a recirculating rat hindlimb perfusion system. TDP-dependent formation of Ang I and II, and an increase in perfusion pressure was shown; ACE inhibition reduced but did not abolish Ang II formation and vasoconstriction. Ang I was converted to Ang II by about 50% during one pass through a hindlimb. This conversion was abolished by ACE inhibition. These data add support to the presence of a functional vascular renin-angiotensin system.

Angiotensin I↗

PubMedDate not supplied

Local angiotensin II generation in the rat heart: role of renin uptake.

To elucidate the local effects of renin in the coronary circulation, we examined local angiotensin (Ang) I and II formation, as well as coronary vasoconstriction in response to renin administration, and compared the effects with exogenous infused Ang I. We perfused isolated hearts from rats overexpressing the human angiotensinogen gene in a Langendorff preparation and measured the hemodynamic effects and the released products. We also investigated cardiac Ang I conversion, including the contribution of non-angiotensin-converting enzyme-dependent Ang II-generating pathways. Finally, we studied Ang I conversion in vitro in heart homogenates. Renin and Ang I infusion both generated Ang II. Ang II release and vasoconstriction continued after renin infusion was stopped, even though renin disappeared immediately from the perfusate. In contrast, after Ang I infusion, Ang II release and coronary flow returned to basal levels. Ang I conversion (Ang II/Ang I ratio) was higher after renin infusion (0.109+/-0.027 versus 0.026+/-0.003, 15 minutes, P<.02) compared with infused Ang I. Remikiren added to the renin infusion abolished Ang I and II; captopril suppressed only Ang II, whereas an AT1 receptor blocker did not affect Ang I and II formation. All the drugs prevented renin-induced coronary flow changes. Total cardiac Ang II-forming activity was only partially inhibited by cilazaprilat (4.1+/-0.1 fmol x min(-1) x mg[-1]) and on a larger extent by chymostatin (2.6+/-0.3 fmol x min(-1) x mg[-1]) compared with control values (5.6+/-0.4 fmol x min(-1) x mg[-1]). We conclude that renin can be taken up by cardiac or coronary vascular tissue and induces long-lasting local Ang II generation and vasoconstriction. Locally formed Ang I was converted more effectively than infused Ang I. Furthermore, the comparison of in vivo and in vitro Ang I conversion suggests that in vitro assays may underestimate the functional contribution of angiotensin-converting enzyme to intracardiac Ang II formation.

Angiotensin I↗