PH o , pH i , and P co 2 in Stimulation of IP 3 and [Ca 2+ ] c in Piglet Cerebrovascular Smooth Muscle

Maria Luiza C. Albuquerque, Charles Leffler

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

Abstract. Hypocapnia produces cerebral vasoconstriction. The mechanisms involved in hypocapnia-induced elevation of vascular smooth muscle tone remain unclear. We addressed the hypothesis that, in cerebrovascular smooth muscle, increases in extracellular pH (pH o ) cause increases in Ins(1,4,5)P 3 and cytosolic calcium ((Ca 2+ ] c ). Superfused primary cultures of piglet cerebral microvascular smooth muscle cells were exposed to artificial CSF (aCSF) of control (pH o 7.4, PCO 2 36 mm Hg), metabolic alkalosis (pH o 7.7, PCO 2 36 mm Hg), or respiratory alkalosis (pH o 7.7, PCO 2 19 mm Hg). Intracellular pH (pH i ) and [Ca 2+ ] c were measured, using BCECF and fura-2, respectively, with dual wavelength spectroscopy. Ins(1,4,5)P 3 was determined by a protein binding assay. Both metabolic and respiratory acidosis treatments increased pH i from the control value of about 7.2 to 7.35. Metabolic and respiratory alkalosis increased Ins(1,4,5)P 3 , as we showed previously. Metabolic and respiratory alkalosis increased [Ca 2+ ] c about 80% and 110%, respectively. Neither Ins(1,4,5)P 3 nor [Ca 2+ ] c increased in cells treated with aCSF that produced control pH o with increased pH i (7.3). In contrast, when pH o increased (7.7), but pH i was maintained at control (7.2), Ins(1,4,5)P 3 increased from 123 pmol/well to 307 pmol/well and [Ca 2+ ] c increased 46%. However, the increase of [Ca 2+ ] c was less than with either respiratory or metabolic alkalosis. Thus, hypocapnia-induced cerebral vasoconstriction could involve production of Ins(1,4, 5)P 3 with resultant elevation in [Ca 2+ ] c . While the Ins(1,4,5)P 3 signal appears to be dependent on an increase in extracellular pH, a role for intracellular pH cannot be completely excluded.

Original languageEnglish (US)
Pages (from-to)226-234
Number of pages9
JournalExperimental Biology and Medicine
Volume219
Issue number3
StatePublished - Dec 1 1998

Fingerprint

Smooth Muscle
Muscle
Respiratory Alkalosis
Hypocapnia
Fura-2
Cell culture
Assays
Cells
Alkalosis
Spectroscopy
Calcium
Wavelength
Vasoconstriction
Respiratory Acidosis
Acidosis
Vascular Smooth Muscle
Protein Binding
Smooth Muscle Myocytes
Spectrum Analysis

All Science Journal Classification (ASJC) codes

  • Biochemistry, Genetics and Molecular Biology(all)

Cite this

PH o , pH i , and P co 2 in Stimulation of IP 3 and [Ca 2+ ] c in Piglet Cerebrovascular Smooth Muscle . / Albuquerque, Maria Luiza C.; Leffler, Charles.

In: Experimental Biology and Medicine, Vol. 219, No. 3, 01.12.1998, p. 226-234.

Research output: Contribution to journalArticle

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N2 - Abstract. Hypocapnia produces cerebral vasoconstriction. The mechanisms involved in hypocapnia-induced elevation of vascular smooth muscle tone remain unclear. We addressed the hypothesis that, in cerebrovascular smooth muscle, increases in extracellular pH (pH o ) cause increases in Ins(1,4,5)P 3 and cytosolic calcium ((Ca 2+ ] c ). Superfused primary cultures of piglet cerebral microvascular smooth muscle cells were exposed to artificial CSF (aCSF) of control (pH o 7.4, PCO 2 36 mm Hg), metabolic alkalosis (pH o 7.7, PCO 2 36 mm Hg), or respiratory alkalosis (pH o 7.7, PCO 2 19 mm Hg). Intracellular pH (pH i ) and [Ca 2+ ] c were measured, using BCECF and fura-2, respectively, with dual wavelength spectroscopy. Ins(1,4,5)P 3 was determined by a protein binding assay. Both metabolic and respiratory acidosis treatments increased pH i from the control value of about 7.2 to 7.35. Metabolic and respiratory alkalosis increased Ins(1,4,5)P 3 , as we showed previously. Metabolic and respiratory alkalosis increased [Ca 2+ ] c about 80% and 110%, respectively. Neither Ins(1,4,5)P 3 nor [Ca 2+ ] c increased in cells treated with aCSF that produced control pH o with increased pH i (7.3). In contrast, when pH o increased (7.7), but pH i was maintained at control (7.2), Ins(1,4,5)P 3 increased from 123 pmol/well to 307 pmol/well and [Ca 2+ ] c increased 46%. However, the increase of [Ca 2+ ] c was less than with either respiratory or metabolic alkalosis. Thus, hypocapnia-induced cerebral vasoconstriction could involve production of Ins(1,4, 5)P 3 with resultant elevation in [Ca 2+ ] c . While the Ins(1,4,5)P 3 signal appears to be dependent on an increase in extracellular pH, a role for intracellular pH cannot be completely excluded.

AB - Abstract. Hypocapnia produces cerebral vasoconstriction. The mechanisms involved in hypocapnia-induced elevation of vascular smooth muscle tone remain unclear. We addressed the hypothesis that, in cerebrovascular smooth muscle, increases in extracellular pH (pH o ) cause increases in Ins(1,4,5)P 3 and cytosolic calcium ((Ca 2+ ] c ). Superfused primary cultures of piglet cerebral microvascular smooth muscle cells were exposed to artificial CSF (aCSF) of control (pH o 7.4, PCO 2 36 mm Hg), metabolic alkalosis (pH o 7.7, PCO 2 36 mm Hg), or respiratory alkalosis (pH o 7.7, PCO 2 19 mm Hg). Intracellular pH (pH i ) and [Ca 2+ ] c were measured, using BCECF and fura-2, respectively, with dual wavelength spectroscopy. Ins(1,4,5)P 3 was determined by a protein binding assay. Both metabolic and respiratory acidosis treatments increased pH i from the control value of about 7.2 to 7.35. Metabolic and respiratory alkalosis increased Ins(1,4,5)P 3 , as we showed previously. Metabolic and respiratory alkalosis increased [Ca 2+ ] c about 80% and 110%, respectively. Neither Ins(1,4,5)P 3 nor [Ca 2+ ] c increased in cells treated with aCSF that produced control pH o with increased pH i (7.3). In contrast, when pH o increased (7.7), but pH i was maintained at control (7.2), Ins(1,4,5)P 3 increased from 123 pmol/well to 307 pmol/well and [Ca 2+ ] c increased 46%. However, the increase of [Ca 2+ ] c was less than with either respiratory or metabolic alkalosis. Thus, hypocapnia-induced cerebral vasoconstriction could involve production of Ins(1,4, 5)P 3 with resultant elevation in [Ca 2+ ] c . While the Ins(1,4,5)P 3 signal appears to be dependent on an increase in extracellular pH, a role for intracellular pH cannot be completely excluded.

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