H. Tao et al., RESPONSE OF CULTURED CEREBRAL-ARTERY SMOOTH-MUSCLE CELLS TO THE NITRIC-OXIDE VASODILATORS, NITROGLYCERIN AND SODIUM-NITROPRUSSIDE, Journal of neurosurgical anesthesiology, 9(1), 1997, pp. 58-64
We characterized the response of soluble guanylyl cyclase in smooth mu
scle cells cultured from cerebral vessels to the nitric oxide (NO)prod
ucing vasodilators, nitroglycerin (NTG) and sodium nitroprusside (SNP)
and determined the ability of these agents to induce tolerance. Smoot
h muscle cells were isolated from porcine basilar, anterior and middle
cerebral, and internal carotid arteries. Following an initial series
of experiments using NTG at various concentrations and times of exposu
re to determine conditions, concentration-response curves of intracell
ular guanosine 3',5'-cyclic monophosphate (cGMP) to NTG and SNP were d
etermined in cells pretreated for 1 h with 100 mu mol NTG to induce to
lerance and compared with response curves in control cells. Basal cGMP
levels were 2.1 +/- 0.4 pmol/mg cell protein (n = 16). Both NTG and S
NP increased cGMP in nontolerant cells, and SNP was more effective. Ma
ximum concentrations of SNP (1 mmol/L) increased cGMP to 163 +/- 5.9 p
mol/mg versus 21 +/- 2.4 pmol/mg for 1 mmol/L NTG (p < 0.01). Cells ma
de tolerant to NTG were unresponsive to NTG up to 1 mmol/L but remaine
d responsive to SNP, However, the response curve to SNP was significan
tly depressed by similar to 25%. Following washout of NTG in tolerant
cells, the response of cGMP to SNP returned to control within 12 h, wh
ile response to NTG required 36 h. Similar experiments were conducted
in cells initially made tolerant to SNP. These results indicate that c
erebral artery smooth muscle cells in culture express a functioning so
luble guanylyl cyclase and the enzymes that are necessary to metaboliz
e NTG to NO. Prolonged exposure of the cells to NTG induced tolerance
as well as cross-tolerance to SNP.