Uptake and metabolism of the novel peptide angiotensin-(1-12) by neonatal cardiac myocytes.
BACKGROUND
Angiotensin-(1-12) [Ang-(1-12)] functions as an endogenous substrate for the productions of Ang II and Ang-(1-7) by a non-renin dependent mechanism. This study evaluated whether Ang-(1-12) is incorporated by neonatal cardiac myocytes and the enzymatic pathways of ¹²⁵I-Ang-(1-12) metabolism in the cardiac myocyte medium from WKY and SHR rats.


RESULTS
The degradation of ¹²⁵I-Ang-(1-12) (1 nmol/L) in the cultured medium of these cardiac myocytes was evaluated in the presence and absence of inhibitors for angiotensin converting enzymes 1 and 2, neprilysin and chymase. In both strains uptake of ¹²⁵I-Ang-(1-12) by myocytes occurred in a time-dependent fashion. Uptake of intact Ang-(1-12) was significantly greater in cardiac myocytes of SHR as compared to WKY. In the absence of renin angiotensin system (RAS) enzymes inhibitors the hydrolysis of labeled Ang-(1-12) and the subsequent generation of smaller Ang peptides from Ang-(1-12) was significantly greater in SHR compared to WKY controls. ¹²⁵I-Ang-(1-12) degradation into smaller Ang peptides fragments was significantly inhibited (90% in WKY and 71% in SHR) in the presence of all RAS enzymes inhibitors. Further analysis of peptide fractions generated through the incubation of Ang-(1-12) in the myocyte medium demonstrated a predominant hydrolytic effect of angiotensin converting enzyme and neprilysin in WKY and an additional role for chymase in SHR.


CONCLUSIONS
These studies demonstrate that neonatal myocytes sequester angiotensin-(1-12) and revealed the enzymes involved in the conversion of the dodecapeptide substrate to biologically active angiotensin peptides.
Hypertension and Vascular Research Center, Wake Forest University School of Medicine, Winston-Salem, North Carolina, United States of America.
Sarfaraz
S
Ahmad
Jasmina
J
Varagic
Brian M
BM
Westwood
Mark C
MC
Chappell
Carlos M
CM
Ferrario
D000808:Angiotensinogen; D000809:Angiotensins / Q000378:metabolism* / Q000493:pharmacokinetics; D000818:Animals; D000831:Animals, Newborn; D006868:Hydrolysis; D007457:Iodine Radioisotopes; D053858:Metabolic Networks and Pathways; D032383:Myocytes, Cardiac / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism* / Q000493:pharmacokinetics; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013379:Substrate Specificity
D000809:Angiotensins; D007457:Iodine Radioisotopes; D010446:Peptide Fragments; C515557:proangiotensin-12, rat; D000808:Angiotensinogen
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