title: Blood-brain barrier to hydrogen ion during acute metabolic acidosis in piglets.
abstract: The present study investigates the integrity of the blood-brain barrier to H+ or HCO3- during acute plasma acidosis in 35 newborn piglets anesthetized with pentobarbital sodium. Cerebrospinal fluid acid-base balance, cerebral blood flow (CBF), and cerebral oxygenation were measured after infusion of HCl (0.6 N, 0.191-0.388 ml/min) for a period of 1 h at a constant arterial PCO2 of 35-40 Torr. HCl infusion resulted in decreased arterial pH from 7.38 +/- 0.01 to 7.00 +/- 0.02 (P less than 0.01). CBF measured by the tracer microsphere technique was decreased by 12% from 69 +/- 6 to 61 +/- 4 ml.min-1.100 g-1 (P less than 0.05). Infusion of 0.6 N NaCl as a hypertonic control had no effect on CBF. Cerebral metabolic rate for O2 and O2 extraction was not significantly changed from control (3.83 +/- 0.20 ml.min-1.100 g-1 and 5.7 +/- 0.6 ml/100 ml, respectively) during acid infusion. Cerebral venous PO2 was increased from 41.6 +/- 2.1 to 53.8 +/- 4.0 Torr by HCl infusion (P less than 0.02) associated with a shift in O2-hemoglobin affinity of blood in vivo from 38 +/- 2 to 50 +/- 1 Torr. Cisternal cerebrospinal fluid pH decreased from 7.336 +/- 0.014 to 7.226 +/- 0.027 (P less than 0.005), but cerebrospinal fluid HCO3- concentration was not changed from control (25.4 +/- 1.0 meq/l). These data suggest that there is a functional blood-brain barrier in newborn piglets, that is relatively impermeable to HCO3- or H+ and maintains cerebral perivascular pH constant in the face of acute severe arterial acidosis. (ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Physiology, University of Pennsylvania School of Medicine, Philadelphia 19104.
authors.forename: L C
authors.initials: LC
authors.lastname: Wagerle
authors.forename: S P
authors.initials: SP
authors.lastname: Kumar
authors.forename: J
authors.initials: J
authors.lastname: Belik
authors.forename: M
authors.initials: M
authors.lastname: Delivoria-Papadopoulos
mesh_terms: D000136:Acid-Base Equilibrium; D000138:Acidosis / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D001639:Bicarbonates / Q000097:blood / Q000134:cerebrospinal fluid; D001794:Blood Pressure; D001812:Blood-Brain Barrier; D002245:Carbon Dioxide / Q000097:blood / Q000134:cerebrospinal fluid; D002560:Cerebrovascular Circulation / Q000187:drug effects; D006851:Hydrochloric Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D010100:Oxygen / Q000097:blood / Q000134:cerebrospinal fluid; D011522:Protons; D013552:Swine
chemical_list: D001639:Bicarbonates; D011522:Protons; D002245:Carbon Dioxide; D006851:Hydrochloric Acid; D010100:Oxygen