Autoradiographic determination of brain pH following middle cerebral artery occlusion in the rat.

Summary:The effects of prostacyclin, nimodipine. and verapamil on local cerebral pH (LCpH) and CBF (LCBF) in middle cerebral artery (MCA)-occluded rats were compared with those in controls and others receiving ni modipine carrier. LCpH and LCBF were determined si multaneously by a double-label autoradiographic tech nique, The infusions were intravenous. started IS min fol lowing the occlusion, and ended at decapitation 4 h postocclusion, The dosages were 0,5 fLg/kg/min for nimo dipine, 40 fLg/kg/min for verapamil, and 5 ng/kg/min for prostacyclin, Cortical LCpH in the MCA territory of control and carrier-infused rats varied between 6,72 ± 0,05 and 6,76 ± 0,05 (means ± SEM), These values were significantly lower than the LCpH in the same structures in the contralateral hemisphere (7,09 ± 0,06; p < 0,05), LCBF on the side of occlusion varied between 54 ± 5 mlllOO g/min for the parietal and 57 ± 7 mJ/IOO g/min for Two metabolic consequences of cerebral isch emia that have received attention recently are the accumulation of lactate with the consequent devel opment of acidosis and the rise in intracellular cal cium concentration (Hass, 1981; Plum, 1983; Raichle, 1983), Both of these processes have been considered harmful to cellular viability and sur vival. Experimentally, excessive lactate accumula tion, usually in the setting of hyperglycemia in as sociation with cerebral ischemia, has resulted in in creased morbidity and mortality (Myers, 1979; Ginsberg et aI. , 1980), intensification of histological

Section: Discussionsupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Cerebral Acidosis in Focal Ischemia: II. Nimodipine and Verapamil Normalize Cerebral pH following Middle Cerebral Artery Occlusion in the Rat

Hakim

1986

“…2 implies prior knowledge of pHe and Ceo Kobatake et al (1984) assumed that pHe = pH p and that C e = C p o Though this assumption may be valid for tumor tissue if the blood-brain barrier (BBB) is deficient, it is prob ably not valid for normal gray and white matter. If…”

Section: Theory and Calcula Nonsmentioning

confidence: 99%

In vivo Measurement of Regional Brain and Tumor pH Using [¹⁴C]Dimethyloxazolidinedione and Quantitative Autoradiography

Arnold

Junck

Rottenberg

1985

Summary: Using [14Cldimethyloxazolidinedione ([14Cl DMO) and quantitative autoradiography, we estimated tissue pH (pH,) and intracellular pH (pHi) in nine regions of the normal rat brain and in intracerebrally implanted RG-2 gliomas, Calculations of regional pH" based on equilibrium tissue and arterial plasma r14CjDMO concen tration, ranged from 6,83 to 6,94; pHi' calculated as suming an extracellular water volume of 0,15 ml/g for gray matter and 0,11 mllg for white matter, ranged from 6,61 to 6,78, No consistent difference was found in pH, or pHi between white and gray matter regions, TumorAccumulating evidence that changes in intracel lular pH (pHj) may accompany or modulate a va riety of biochemical and biophysical processes (Busa and Nuccitelli, 1984) has led to a renewed interest in the measurement of pHj. Using 14C-la beled dimethyloxazolidinedione (DMO) and quan titative autoradiography. we obtained preliminary measurements of regional brain and tumor pH in normal rats and in rats with leptomeningeal tumor. In both control and tumor-bearing animals. white matter was slightly but consistently more acidic than gray matter, whereas tumor was more alkaline than any brain region examined (J unck et al.. 1981). Similar preliminary results were obtained in rats with intracerebrally implanted RG-2 gliomas (Rot tenberg et aI., 1984). These findings are somewhat surprising, given the characteristically high rate of 369tissue water content was determined by drying to con stant weight, and extracellular space water volume (Ve) was estimated with r14Clsucrose in nephrectomized rats using quantitative autoradiography. Tumor pH, ranged from 7.08 to 7,18, For Ve = 0.17 (measured), pH; was 6.94-7 ,06; for Ve = 0,30 (assumed), the corresponding range for pHi was 6,63-6,90, Thus. the RG-2 glioma is not more "acidic" than adjacent brain tissue and its "al kaline" pH, probably reflects a large extracellular water content and plasma-like extracellular pH. Key Words: Brain tumor pH-Quantitative autoradiography, anaerobic glycolysis and lactic acid production in tumor tissue (Warburg, 1930).The present study was undertaken to (a) extend our previous measurements of regional brain/tumor pH to intracellular pH, (b) define the uncertainty in MATERIALS AND METHODSRG-2 tumor cells were implanted intracerebrally into male CDF rats using a freehand injection technique (Gro othuis et aI., 1983h). The cells. obtained from a frozen stock. were thawed and grown in tissue culture before being pelleted and resuspended for injection in methyl cellulose solution; � 10 -4 cells were injected in a total volume of 2 , .. d. Representative tumored animals were autopsied at 2 .. to 3 .. day intervals following an intravenous injection of Evans blue dye to aid in the identification of

“…The DMO technique has been used in normal rats and after occlusion of the middle cerebral artery (Kobatake et al, 1984;Hakim, 1986) but not, to our knowledge, under the circumstances of the present study. Since the methods appear to be valid after middle cerebral artery occlusion, an insult more likely than the conditions of the present study to have an adverse effect on the assumptions that un derlie the DMO technique, we believe that this is a warranted extension of the method.…”

Section: Application Of Dg and Dmo Techniques To The Modelmentioning

confidence: 94%

Effects of Moderate Hypoxemia and Unilateral Carotid Ligation on Cerebral Glucose Metabolism and Acid-Base Balance in the Rat

Lockwood

Peek

Izumiyama

et al. 1989

The pathogenesis of brain injury or dysfunction following hypoxic or ischemic episodes is an issue of considerable importance. The neurochemical re sponses to hypoxia and ischemia are complex, and a number of authors have suggested that anaerobic metabolism of exogenous glucose to form lactic acid is a critical element in determining whether permanent cerebral injury occurs. This hypothesis dates to reports of Myers and Yamaguchi (1977) in which cardiac arrest during hyperglycemia was as sociated with more extensive neurological injury than cardiac arrest during normoglycemia. Rehn crona et al. (1980) found that if the lactate concen- tration exceeded 20-25 mmol/kg, recovery to a nor mal energy state was precluded. Subsequent re ports have supported this hypothesis (Siesj6, 1985;Rehncrona, 1986).The effects of hypoxia on glucose metabolism are more complex than the commonly held belief that anaerobic glycolysis causes acidosis owing to the hydrolysis of lactic acid. Gevers (1977) pointed out that the production of lactate itself does not lead to an obligatory co-production of hydrogen ions and a fall in pH, since the net products of anaerobic gly colysis are two lactate ions and two MgATp 2 -ions.Acidosis is caused by the concurrent net hydrolysis of ATP, which produces two H+ ions. Although the net reaction of anaerobic glycolysis, ATP hydroly sis, and synthesis, always yields two lactate ions and two H+ ions from each glucose molecule, the concentration of dissociated hydrogen ions is af fected by the pH of the reaction system, the mag nesium ion concentration, and the substrate (glu cose or glycogen) (Hochachka and Mommsen,