THE DISTRIBUTION OF GUANIDINE-ADENOSINE TRIPHOSPHATE PHOSPHOTRANSFERASES AND ADENOSINE TRIPHOSPHATASE IN ANIMALS FROM SEVERAL PHYLA.
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Adenosine Triphosphatases↗
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[Effects of normal lymph on myeloperoxidase activity and adenosine triphosphatase in rats with endotoxic shock].
OBJECTIVE: To observe the effects of exogenous normal lymph on myeloperoxidase (MPO) and adenosine triphosphatase (ATPase) activities of lung homogenate in rats with endotoxic shock caused by lipopolysaccharide (LPS), and to preliminarily discuss its mechanisms. METHODS: Forty male Wistar rats were randomly divided into four groups: endotoxin group, lymph group, plasma group and control group. The rats in the preceding three groups were injected intravenously with LPS (5 mg/kg. bw, iv) to replicate endotoxic shock model. LPS was replaced by equal volume of normal saline in the control group. Fifteen minutes later, lymph without cell components was infused in lymph group. The amount of lymph was 1/15 of blood volume. In plasma group, lymph was replaced by plasma, and in normal and endotoxin groups, lymph were replaced by normal saline. Four hours after the infusion of LPS, lung homogenate in a concentration of 10% was prepared. The activities of MPO and ATPase were determined in lung homogenate. RESULTS: Compared with control group, the activities of MPO in lung homogenate of endotoxin group and plasma group were significantly increased while the activities of ATPase were significantly lower (P<0.05 or P<0.01). The activity of MPO in lung homogenate of lymph group was significantly higher, while Na(+)-K(+)-ATPase activity was significantly lower than those of control group (both P<0.05). The activities of Ca(2+)-ATPase, Mg(2+)-ATPase and Ca(2+)-Mg(2+)-ATPase in lymph group showed no statistically significant differences compared with those of control group (all P>0.05), but when compared with the endotoxin group and plasma group, the activity of MPO in lung homogenate was significantly lower (both P<0.01) and the activities of 4 kinds of ATPase were significantly higher (P<0.05 or P<0.01). CONCLUSION: The results demonstrate that exogenous normal lymph could ameliorate the lung injury as a result of endotoxic shock, and its mechanism might relate to reduction of activity of the polymorphonuclear leucocyte (PMN) and enhancement of the activity of ATPase.
Adenosine Triphosphatases↗
Cardiac Na+, K+-adenosine triphosphatase inhibition by ouabain and myocardial sodium: a computer simulation.
The major evidence against the hypothesis that Na+, K+-adenosine triphosphatase (Na+, K+-ATPase) inhibition is the mechanism of the positive inotropic action of digitalis is that the myocardial sodium content does not increase at the time of the inotropic response. In order to understand the relationship between sodium pump inhibition and myocardial sodium content, a computer simulation of the intracellular sodium concentration ([Na+]i) during a cycle of myocardial function was performed. The model for the computer simulation is a small compartment adjacent to the inner surface of the sarcolemma. The change in [Na+]i in this compartment is determined by the rate of sodium influx (published data utilized) and the rate of active sodium transport was estimated from the activities of partially purified dog heart Na+, K+-ATPase preparations assayed with various concentrations of sodium and ouabain. The initial rapid sodium influx results in maximal sodium pump activation, but the pump activity decreases with time as the [Na+]i decreases. Thus, the sodium pump functions at a rate close to its maximal velocity during the initial phase of each cycle but at reduced rates during the later phase. Inhibition of Na+, K+-ATPase by ouabain decreases the maximal velocity during the intiial phase of each cycle but at reduced rates during the later phase. Inhibition of Na+, K+-ATPase by ouabain decreases the maximal velocity of the sodium pump but increases the time in each cycle at which the sodium pump operates at its highest possible rate under these conditions, i.e., a rate close to the inhibited maximal velocity. A 40% inhibition of Na+, K+-ATPase activity, caused by inotropic concentrations of ouabain, increases the peak [Na+]i but fails to cause intracellular sodium accumulation since [Na+]i approaches control levels before the beginning of the next cardiac cycle. With greater enzyme inhibition, caused by arrhythmic concentrations of ouabain, [Na+]i fails to return to the precycle level and thus each subsequent cycle causes a progressive accumulation of myocardial sodium. Computer simulation predicts that a positive inotropic concentration of ouabain causes a myocardial sodium accumulation at a high heart rate but not at a lower heart rate. This was confirmed by experiments with Langendorff preparations of guinea-pig hearts. It is concluded that a moderate sodium pump inhibition by inotropic concentrations of ouabain enhances the intracellular sodium transient (a transient increase in intracellular sodium concentration associated with each membrane excitation) but does not cause a significant myocardial sodium accumulation at normal heart rates. A progressive myocardial sodium accumulation occurs only when the degree of Na+, K+-ATPase inhibition exceeds a critical magnitude.
Adenosine Triphosphatases↗
Method for isolation of Escherichia coli mutants with defects in the proton-translocating sector of the membrane adenosine triphosphatase complex.
A technique for selecting mutants of Escherichia coli in which the proton-translocating sector of the adenosine triphosphatase (ATPase) complex has been inactivated is reported. The procedure uses a strain of E. coli (NR-70) lacking the extrinsic (F1) sector of the ATPase complex and which in consequently permeable to protons (B. P. Rosen, J. Bacteriol. 116:1124--1129, 1973). After growing strain NR-70 under noninducing conditions for the lac operon, cells were mutagenized and plated on minimal medium containing low concentrations of lactose. Several mutants of strain NR-70 were isolated as large colonies on these plates, apparently because they could concentrate lactose more efficiently. A description of one of the mutants, strain KW-1, is reported here. The most distinguishing difference in growth properties of the two strains was that, when transferred to medium containing low concentrations of lactose, strain KW-1 induced the lac operon with a shorter lag time than strain NR-70. The mutation in strain KW-1 leading to more rapid growth on lactose was cotransducible with the asn and unc loci, at 83 min on the E. coli genetic map. Intact cells of strain KW-1 actively transported L-proline as well as did wild-type cells, whereas cells of strain NR-70 were markedly deficient in L-proline transport. The improvement in the transport capacity of strain KW-1 correlated with a marked decrease in proton permeability relative to that of strain NR-70. Based on an acid-base pulse technique that measured the proton conductance of the membranes of intact cells, strain NR-70 was at least 10 times more permeable to protons than was the wild type, whereas strain KW-1 was only 2 times more permeable. The transport properties and proton conductance were also compared with membrane vesicles prepared by osmotic shock. With either D-lactate or ascorbate-N-methylphenazonium methosulfate as respiratory substrates, vesicles of strain KW-1 transported L-proline much more rapidly than did vesicles of strain NR-70, but still at rates less rapid than those of the wild type. The passive proton conductance of the membrane vesicles was quantitated by measuring the rate of H+ influx into vesicles in response to a valinomycin-generated K+ diffusion potential. The proton permeability of vesicles of strain KW-1 was reduced 1.5-fold relative to vesicles of strain NR-70, but these vesicles were still four times more permeable to protons than was the wild type. Vesicles of strain KW-1 corresponded to wild-type vesicles treated with 0.5 micrometer carbonylcyanide m-chlorophenylhydrazone (CCCP) and vesicles of strain NR-70 corresponded to wild-type vesicles treated with 1.4 micrometer CCCP. Treatment of wild-type vesicles with these concentrations of CCCP caused decreases in transport comparable to those observed in the mutants. Strain KW-1 lacked ATPase activity. Cross-reacting material to F1-ATPase was not found in strain KW-1 by double immunodiffusion analysis.
Adenosine Triphosphatases↗
Postmortem changes in the level of calcium pumping adenosine triphosphatase in rat heart sarcoplasmic reticulum.
The activity of calcium pumping adenosine triphosphatase (Ca2+-ATPase) in cardiac sarcoplasmic reticulum plays a pivotal role in myocardiac contraction-relaxation. The Ca2+-ATPase activity is controlled by phosphorylation and dephosphorylation of a sarcoplasmic reticulum protein "phospholamban" in response to neurotransmitters and drugs. To clarify the role of Ca2+-ATPase in the development of cardiac rigor mortis, we examined the changes of cardiac rigidity and cardiac sarcoplasmic reticulum Ca2+-ATPase activity up to 5 h after the decapitation of rats. Fifteen minutes after decapitation, the rats showed a cardiac rigidity on left ventricles. After 30 min, rigidity was obvious over the whole heart. After 1 h, the rigidity reached a high degree which was maintained for the rest of the observation period. On the other hand, the Ca2+-ATPase activity controlled by phosphorylation and dephosphorylation of phospholamban did not change for the whole observation period (5 h). Another Ca2+-ATPase activity representing the total amount of Ca2+-ATPase in sarcoplasmic reticulum gradually decreased. The data suggest that no significant phosphorylation or dephosphorylation of phospholamban occurs for a short time, at least for 5 h, after death and that the Ca2+-ATPase tends to relax the myocardium against the development of cardiac rigor mortis.
Animals↗
An in situ cytochemical evaluation of blood-brain barrier sodium, potassium-activated adenosine triphosphatase polarity.
It is presently believed that sodium, potassium-activated adenosine triphosphatase (Na+, K+-ATPase) is localized on the abluminal plasma membrane of brain endothelial cells. But there have been contrary reports from some cytochemical studies. We examined the localization of the enzyme in rat cerebral microvessel endothelium using the in situ model originally employed to establish the abluminal polarity concept. Alterations in fixation and incubation media from the original reports were conducted to determine the effect on localization pattern. With the Ernst indirect incubation method as originally used, three types of localization patterns were obtained: abluminal only, luminal only, and on both surfaces of endothelial cells. With the direct incubation method of Mayahara, reaction product was seen on both surfaces. Reduction in fixation time followed by the use of the indirect incubation method resulted in a complete loss of the reaction product. The same reduction in fixation time followed by the use of the direct method did not alter the localization pattern of the enzyme. Our results demonstrated that Na+, K+-ATPase is localized on both surfaces of brain endothelial cells. The localization pattern of Na+, K+-ATPase is significantly dependent upon fixation and the incubation medium used in the in situ model. Data discrepancies for the enzyme as reported in the literature appear to be caused by differences in cytochemical protocols, rather than the biological reasons advocated by other investigators. We conclude that past cytochemical reports of blood-brain barrier (BBB) Na+, K+-ATPase abluminal localization were incomplete. The currently held abluminal polarity theory of the enzyme needs to be reexamined. Past basic and clinical cytochemical studies of BBB Na+, K+-ATPase should be viewed and interpreted with caution.
Animals↗
Decreased calcium pump adenosine triphosphatase in red blood cells of hypertensive subjects.
Several operationally defined adenosine triphosphatase (ATPase) activities were determined in vitro in red blood cell lysates of normotensive or hypertensive humans: Mg2+-ATPase, Na+,K+-ATPase, and Ca2+ pump ATPase, the latter in the calmodulin-activated and basal states. Basal Ca2+ pump ATPase was defined as the Ca2+-activated ATPase resistant to 10(-4) M trifluoperazine. Subjects were part of a double-blind study in which treatment was divided into several phases: baseline (4 weeks), placebo or calcium (1 g elemental calcium/day, 8 weeks), placebo washout (4 weeks), placebo or calcium (1 g elemental calcium/day, 8 weeks). Irrespective of the phase of treatment, the basal Ca2+ pump ATPase activity in red blood cell lysates of 36 hypertensive subjects was significantly less than that in lysates from 18 normotensive subjects. Other ATPase activities did not differ significantly, although all ATPases tended to be decreased in hypertension. The data are consistent with previous reports of altered membrane Ca2+ binding and transport in hypertension, but the precise changes are not elucidated.
Adult↗
Effects of several selected odorants on the sodium- and potassium-dependent adenosine triphosphatase activities of two different chicken olfactory tuberinals.
The NaK-adenosine triphosphatase (ATPase)-rich nerve-ending particle preparations (B fractions) of the epithelial tissue of chicken olfactory tubercle and the olfactory main concha were isolated by differential centrifugation. These tissues were exposed to the following odorants: 2-nonanone, 1-nonanol, 1-octanol, (+)2-octanol, and (-)2-octanol. There was a significant stimulation of NaK-ATPase by 2-nonanone (1 x 10(-3) M) in the B fraction of the olfactory tubercle and olfactory main concha. The NaK-ATPase increased significantly in the B fraction response of the olfactory main concha with 1 x 10(-3) M of 1-octanol but NaK-ATPase declined significantly in the presence of 1 x 10(-3) M of 1-nonanol. Both optical and structural isomers of odorants were shown to elicit different responses in NaK-ATPase activity. It is proposed that interactions between the odorant molecules and the membrane bound NaK-ATPase complex lead to recognition of odor by chickens.
1-Octanol↗
Na+ transport by the (Na+)-stimulated adenosine triphosphatase.
We have previously shown that the (Na+ and K+)-stimulated adenosine triphosphatase from canine kidney reconstituted into phospholipid vesicles is capable of K+-independent transport of Na+ against a concentration gradient (Forgac, M., and Chin, G. (1981) J. Biol. Chem. 256, 3645-3646). The Na+ dependence of the stoichiometry of this process has been investigated and suggests that Na+ ions can be bound and transported by the sites normally occupied by K+. Measurement of the membrane potential generated during active Na+ uptake by [3H]triphenylmethylphosphonium ion distribution gave a value of 50 mV (positive inside). The electrogenicity of Na+ transport is sufficient to explain the observed uptake of an approximately equivalent amount of Cl-. We have also measured Na+ transport into reconstituted vesicles containing neither Na+ nor K+. Na+ uptake was half-maximal at an external Na+ concentration of 1 mM and was accompanied by a less than equivalent amount of Cl- uptake. In order to determine whether protons might also be moving in this system, the intravesicular pH was measured with the pH-sensitive fluorescent probe 1-hydroxypyrene-3,6,8-trisulfonic acid. Active Na+ uptake was accompanied by proton efflux, the amount of proton movement depending on the counterion present.
Animals↗
Microcalorimetry as an immunological tool: preliminary studies with beef heart mitochondrial adenosine triphosphatase and its antiserum.
The calorimetric technique was applied to a complex immunological system based upon purified beef heart mitochondrial adenosine triphosphatase (ATPase). Whole serum containing antibodies to the ATPase was obtained from a rabbit and used to study the antigen-antiserum interaction in comparison with control serum pooled from 50 non-immune rabbits. The results suggest that the immunological interaction may be accompanied by complex processes which were not detectable by other immunological methods. It was shown that kinetic analysis of the calorimetric data may resolve an apparently complex process of interaction into different component stages of reaction. The advantages of this type of application of calorimetry are discussed.
Adenosine Triphosphatases↗
Secretion of a lactone-hydrogenated ouabain-like effector of sodium, potassium-adenosine triphosphatase activity by adrenal cells.
Ouabain-like factor (OLF), a mammalian cardenolide, is a counterpart to plant-derived ouabain and is found in the adrenal, hypothalamus, and blood of several mammalian species. We now report the existence of a mammalian lactone-hydrogenated ouabain-like factor (dihydro-OLF) in secretions from cultured mouse adrenal Y-1 cells. Dihydro-OLF structurally and functionally mimics plant-derived dihydroouabain. We measured both OLF and the newly discovered dihydro-OLF using five independent techniques: immunoreactivity with two specific antisera, one against ouabain and one against dihydroouabain; chromatographic mobility; spectral absorbance characteristics; and concentration-dependent inhibition and phosphorylation of Na,K-adenosine triphosphatase. All measured physical attributes of dihydro-OLF mimic those of plant-derived dihydroouabain, including a spectral shift maxima, 220 nm (OLF) to 196 nm (dihydro-OLF), with appropriately decreased molar absorptivity. Dihydro-OLF (IC50 = 590 nM) is a 10-fold less potent Na+,K+-adenosine triphosphatase inhibitor than its oxidized mammalian counterpart OLF (IC50 = 60 nM), just as dihydroouabain is less potent than ouabain. Dihydro-OLF is also 3-fold more potent than a recently identified isomer of plant-derived dihydroouabain (IC50 = 1,700 nM). Using antiouabain and antidihydroouabain antisera we estimate that 3 x 10(7) mouse adrenal Y-1 cells secreted 1.3 ng OLF and 8.9 ng dihydro-OLF. The relative abundance of dihydro-OLF is consistently greater than that of its oxidized form, OLF, in bovine adrenals (22-fold), human serum (13-fold), and secretions from cultured mouse Y-1 cells (5-fold). The discoveries of OLF, OLF-genin, and now dihydro-OLF constitute an intriguing structural polymorphism probably involved in the synthesis, regulation, and metabolic control of these new hormone-like compounds.
Adrenal Glands↗
Effect of thyrotropin-releasing hormone on Na(+)-K(+)-Adenosine triphosphatase activity following experimental spinal cord trauma.
The effect of thyrotropin-releasing hormone (TRH) on spinal cord Na(+)-K(+-adenosine triphosphatase (Na+-K+-ATPase) activity after spinal cord injury was evaluated in rats. The rats were injured by compression of the cord at T-10 for 1 minute with a 50-g clip. Saline in the placebo group (n = 8) and TRH (0.6 mg per dose) in the TRH group (n = 9) were administered intraperitoneally as bolus injections in two doses, at 45 and 120 minutes after the injury. The Na(+)-K(+)-ATPase activity level in the TRH group was significantly higher (p = 0.024) than in placebo group. These results indicate a possible role for TRH treatment in spinal cord injury.
Adenosine Triphosphatases↗
Solubilization of adenosine triphosphatase associated with herpes simplex virus.
The nonionic detergent Triton X-100 was used for the solubilization of Mg2"ependent adenosine triphosphatase (Mg2+ATPase) associated with mature herpes simplex virus (HSV) particles purified from infected rabbit lung (ZP) cells. The solubilization was the best at pH 8.1 with a Triton X-100 to protein ratio of 10. The solubilized enzyme splited ATP at the greatest rate at pH from 7.9 to 8.6. pH greater than 8.6 during extraction had a deleterious effect on the enzyme. In the presence of NaCl significantly more proteins were extracted but the enzyme was slightly inhibited. No enhancement of the enzyme activity after detergent treatment and the relatively mild conditions for extraction indicated that the enzyme is not too firmly associated with the surface of the herpesvirions.
Adenosine Triphosphatases↗
Chemo-architectonic studies in a submammalian brain. Adenosine triphosphatase and simple esterase in the diencephalon and mesencephalon.
The present report deals with the histo-enzymological mapping of adenosine triphosphatase and simple esterase in the diencephalon and mesencephalon of Uromastix hardwickii. The enzymatic make-up, in both cases, does not differ markedly in the various nuclei; few variations, of course, occur in some midbrain areas like pretectal nuclei. The latter are intensely positive for ATPase, while these nuclei are moderate to simple esterase. Nevertheless, one of the most interesting results pertaining to simple esterase activity is of a high order in the fiber tracts in comparison to ATPase. The other interesting feature relates to the fact that generally intensely positive nuclei, in ATPase preparations, are those which have extensive efferent fibres. The metabolic significance of high degree of ATPase activity vis-a-vis extensive efferent connections has been exhaustively discussed, besides the possible significance of the general data obtained.
Adenosine Triphosphatases↗
Characteristics of inhibition of human renal adenosine triphosphatases by cisplatin and chloroplatinic acid.
Cisplatin and chloroplatinic acid were examined for in vitro inhibition of human renal microsomal adenosine triphosphatases activated by Na+ + K+ + Mg2+, Mg2+, and Ca2+. The concentrations of cisplatin to inhibit 50% of activity (I50) were approximately 7 X 10(-4) M for all enzymes studied; I50s of chloroplatinic acid were on the order of 10(-5) M for Na+ + K+ + Mg2+ ATPase and Ca2+ ATPase and 10(-7) M for Mg2+ ATPase in the presence of Na+ + K+ + ouabain. Inhibition of Na+ + K+ + Mg2+ ATPase by cisplatin or chloroplatinic acid was reversible and was not altered by varying Na+, K+, or Mg2+ concentrations; ATP or MgATP increased inhibition by cisplatin but not by chloroplatinic acid; acidic pH of 6.8 lowered inhibition by chloroplatinic acid but not by cisplatin. Cysteine, glutathione (-SH reagents), and ascorbic acid greatly reduced inhibition of all enzymes studied by chloroplatinic acid; in the case of cisplatin, -SH reagents had only a minimal protective effect but ascorbic acid somewhat increased inhibition. Methionine greatly increased inhibition by cisplatin but provided minimal protection in the case of chloroplatinic acid. In view of the hypothesis that inhibition of renal Na+ + K+ ATPase may be associated with tubular damage, the inhibition of Na+ + K+ ATPase may be relevant to the mechanism of platinum toxicity.
Adenosine Triphosphatases↗
Unique enzymes of purified microsomes from pig fundic mucosa. K+-stimulated adenosine triphosphatase and K+-stimulated pNPPase.
Microsomal fractions from homogenates of pig gastric fundic mucosa showed high levels of K+-stimulated adenosine triphosphatase (ATPase) and K+-stimulated phosphatase. Similar preparations from antral mucosa showed virtually no such activity. Because of mitochondrial contamination the fundic microsomes were further separated by sucrose density gradient centrifugation. A low density band of membranes (peak 1.12 to 1.13 g per ml) possessed all of the K+-stimulated enzyme activities. Morphological features and the abundant glycoproteins of the low density microsomes suggested they might be derived from the tubulovesicles of oxyntic cells. Mitochondrial and ribosomal markers were associated with membranes with much higher densities (greater than 1.22). The K+-stimulated ATPase has a pH optimum of 7.5 and required Mg++, but neither Na+ nor ouabain had any appreciable effect on the activity. Stimulation of basal ATPase by K+ ranged from 1.5 to 3.0-fold with an apparent Ka for activation between 0.2 to 0.4 mM K+. Addition of various K+ ionophoretic substances (e.g., gramicidin) produced further stimulation of K+-ATPase up to 6 times the basal rate. The mean activities for seven separate preparations of purified low density pig fundic microsomes were as follows (micromoles of ATP hydrolyzed per mg protein per hr +/- SEM); basal ATPase, 15.8 +/- 2.8; plus 10 mM K+, 29.3 +/- 4.5; plus 10 mM K+ and 10(-5) M gramicidin, 45.2 +/- 5.2. Neither the basal ATPase nor the K+-stimulated rates were altered by HCO3- or Cl-. The occurrence of these active and unique enzyme activities in the oxyntic region of gastric mucosa suggest some relation with secretory activity. Possible functional roles are discussed.
4-Nitrophenylphosphatase↗
Adenosine triphosphatases of rat pancreatic islets: comparison with those of rat kidney.
Electrolyte fluxes are fundamental to normal endocrine pancreatic function. Adenosine triphosphatases (ATPases) are enzyme systems believed to modulate electrolyte movements across membranes in a number of cell types. This study was undertaken to measure cation-dependent ATPases of rat pancreatic islets. In addition, we compared effects of substances which influence endocrine pancreatic function upon ATPases in homogenates of islets and kidney, the latter being a tissue which would not be expected to have a stimulus-secretion response to substances which activate islets. Both tissues were generally similar with respect to apparent Michaelis constant (ATP) of Na(+)K(+)ATPase, Mg(++)ATPase, and Ca(++)ATPase. In islets and kidney, Na(+)K(+)ATPase specific activity was increased when the Na:K ratio was lowered from 250:1 (175:0.7 mM) to 5:1 (100:20 mM). Inhibition of Na(+)K(+)ATPase at either Na:K ratio by ouabain, an activator of secretion, and enhancement of the high-ratio Na(+)K(+)ATPase by diphenylhydantoin, an islet secretory inhibitor, were also common to both tissues. Because both inhibition and enhancement of Na(+)K(+)ATPase could be studied at the high Na:K ratio, we examined the effect of regulators of secretion upon the activity of this enzyme. Like ouabain, substances which induce or support islet secretion, glucose 16 mM or 3.3 mM, arginine 14.2 mM (with 3.3 mM glucose), or Ca(++) 1 mM, inhibited high-ratio islet Na(+)K(+)ATPase. Like diphenylhydantoin, the inhibitors of insulin secretion, diazoxide 0.22 mM, or NH(4)Cl 16 mM, enhanced this islet ATPase. Neither valine, which is non-secretogenic, nor arginine without glucose, which is a weak secretagogue, had any effect upon islet Na(+)K(+)ATPase. We examined the effect of these substances upon other cation-dependent islet ATPases. Ca(++) inhibited Mg(++)ATPase, and glucose inhibited Ca(++)ATPase. Leucine, 22.9 mM, which induces insulin secretion in the absence of glucose, suppressed islet Ca(++)ATPase and had no effect upon high-ratio Na(+)K(+)ATPase. In contrast to the observations in the islets, most substances which influence islet function had no effect on kidney ATPases, or effects which were different from those seen in islets. Except for ouabain, none of these substances influenced the three kidney ATPases in a manner similar to that seen with islets. These findings support the hypothesis that cation-dependent ATPases are involved in specificity of islet response to substances which influence endocrine pancreatic activity.
Adenosine Triphosphatases↗
Cytochemical study of the distribution of adenosine triphosphatase in the pancreas of the dog.
Dog pancreatic tissue, incubated in a modified Wachstein-Meisel medium, showed two different adenosine triphosphatase activities. One of them is located at the apical border of the cells lining the intralobular ducts and of the centroacinar cells and is stimulated by HCO3-, depressed by SCN- and OCN- and completely abolished by CN-. The other is located at the intracellular clefts of the epithelium lining the interlobular ducts and is stimulated by Mg++. These findings correlate well with the results of incubation of homogenates of fresh and fixed tissues. Their significance with respect to the role of different segments of the duct system in the formation of the pancreatic juice is discussed.
Adenosine Triphosphatases↗