TY - JOUR
T1 - Hypoglycemia selectively abolishes hypoxic reactivity of pial arterioles in piglets
T2 - Role of adenosine
AU - Park, T. S.
AU - Gonzales, E. R.
AU - Shah, A. R.
AU - Gidday, J. M.
PY - 1995
Y1 - 1995
N2 - Episodes of hypoxia often occur in hypoglycemic newborns, but it is not known whether dysfunctions in cerebrovascular regulation contribute to brain injury incurred by these affected neonates. We tested the hypotheses that 1) perinatal hypoglycemia impairs cerebrovascular responses to hypoxia and 2) a reduced vascular smooth muscle sensitivity to adenosine accounts for this impairment. Responses of 25- to 50-μm-diam pial arterioles were determined using the cranial window technique in isoflurane-anesthetized newborn piglets < 5 days of age. Hypoxia (arterial PO2 = 28 ± 1 mmHg) caused a 47 ± 5% increase (P = 0.0008) in arteriolar diameter, 89% of which could be blocked by prior superfusion of the window space with the preferential A2-adenosine receptor antagonist 3,7-dimethyl-1-propargylxanthine (DMPX; 50 μM). Insulin- induced hypoglycemia (blood glucose = 18 ± 1 mg/dl without isoelectric electroencephalogram) caused a 31 ± 5% increase (P = 0.002) in arteriolar diameter; however, no additional dilatative response to hypoxia (arterial PO2 = 28 ± 1 mmHg) could be elicited in these animals. Arteriolar dilation of 41 ± 6% (P = 0.002) induced by superfusion of 20 μM adenosine under normoglycemic conditions was also completely abolished after the animals were rendered hypoglycemic. Unlike the response to hypoxia and adenosine, hypoglycemia only attenuated prostanoid-dependent dilations to hypercapnia (arterial PCO2 = 68 ± 3 mmHg) by 55 ± 9%. These results indicate that, in the newborn, hypoglycemia selectively abolishes hypoxic reactivity through an impairment in adenosine-mediated cerebrovascular dilation.
AB - Episodes of hypoxia often occur in hypoglycemic newborns, but it is not known whether dysfunctions in cerebrovascular regulation contribute to brain injury incurred by these affected neonates. We tested the hypotheses that 1) perinatal hypoglycemia impairs cerebrovascular responses to hypoxia and 2) a reduced vascular smooth muscle sensitivity to adenosine accounts for this impairment. Responses of 25- to 50-μm-diam pial arterioles were determined using the cranial window technique in isoflurane-anesthetized newborn piglets < 5 days of age. Hypoxia (arterial PO2 = 28 ± 1 mmHg) caused a 47 ± 5% increase (P = 0.0008) in arteriolar diameter, 89% of which could be blocked by prior superfusion of the window space with the preferential A2-adenosine receptor antagonist 3,7-dimethyl-1-propargylxanthine (DMPX; 50 μM). Insulin- induced hypoglycemia (blood glucose = 18 ± 1 mg/dl without isoelectric electroencephalogram) caused a 31 ± 5% increase (P = 0.002) in arteriolar diameter; however, no additional dilatative response to hypoxia (arterial PO2 = 28 ± 1 mmHg) could be elicited in these animals. Arteriolar dilation of 41 ± 6% (P = 0.002) induced by superfusion of 20 μM adenosine under normoglycemic conditions was also completely abolished after the animals were rendered hypoglycemic. Unlike the response to hypoxia and adenosine, hypoglycemia only attenuated prostanoid-dependent dilations to hypercapnia (arterial PCO2 = 68 ± 3 mmHg) by 55 ± 9%. These results indicate that, in the newborn, hypoglycemia selectively abolishes hypoxic reactivity through an impairment in adenosine-mediated cerebrovascular dilation.
UR - http://www.scopus.com/inward/record.url?scp=0028930635&partnerID=8YFLogxK
U2 - 10.1152/ajpheart.1995.268.2.h871
DO - 10.1152/ajpheart.1995.268.2.h871
M3 - Article
C2 - 7864214
AN - SCOPUS:0028930635
SN - 0363-6135
VL - 268
SP - H871-H878
JO - American Journal of Physiology - Heart and Circulatory Physiology
JF - American Journal of Physiology - Heart and Circulatory Physiology
IS - 2 37-2
ER -