Adenosine dephosphorylates myosin light chain in primary cultures of vascular smooth muscle cells from normotensive and spontaneously hypertensive rats.
OBJECTIVE
The aim was to determine whether vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) respond differently to adenosine than those from normotensive Wistar-Kyoto (WKY) rats.


METHODS
Confluent primary cultures of VSMC derived from SHR and WKY aorta and mesenteric arteries and cerebral arteries were used. The effect of adenosine upon cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) formation and the phosphorylation of myosin light chain (MLC) was studied.


METHODS
MLC phosphorylation was estimated by subjecting VSMC extracts incubated with 32P to gel electrophoresis, followed by autoradiography and laser densitometry. cAMP and cGMP levels were measured by radioimmunoassay.


RESULTS
Baseline MLC phosphorylation levels were not significantly different in SHR and WKY VSMC. Adenosine caused dephosphorylation of MLC in a time- and dose-dependent manner. A maximal response of approximately 40% below control values was observed 5 min after addition of 10(-5) mol/l adenosine in SHR and WKY VSMC with no significant difference between the two strains. The maximally effective concentration of 10(-5) mol/l adenosine evoked increases in both cAMP and cGMP in VSMC from SHR and WKY rats to the same degree.


CONCLUSIONS
We conclude that the overall ability of VSMC to relax, as evidenced by a marked decrease in MLC phosphorylation in response to adenosine, is unaltered in SHR.
Benze
J
J
Medical Research Council/University Circulation Research Unit, University of Witwatersrand Medical School, Johannesburg, South Africa.
Griffith
V J
VJ
Yang
H Y
HY
Rosendorff
C
C
D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D002478:Cells, Cultured / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D000242:Cyclic AMP / Q000032:analysis / Q000378:metabolism; D006152:Cyclic GMP / Q000032:analysis / Q000378:metabolism; D006973:Hypertension / Q000378:metabolism; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D009218:Myosins / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
D000242:Cyclic AMP; D009218:Myosins; D006152:Cyclic GMP; D000241:Adenosine