1. An adenosine triphosphatase membrane system, dependent on Mg(2+) and activated further by Na(+)+K(+), was prepared from goldfish anterior intestine by differential centrifugation of homogenized intestinal scrapings. 2. The affinity of this preparation for Na(+) in the presence of K(+)+Mg(2+), for K(+) in the presence of Na(+)+Mg(2+) and for Mg(2+) alone, measured at 37 degrees , did not depend on the previous environmental temperature of the fish. When Na(+)+K(+) were added to preparations from 8 degrees -acclimatized fish the affinity for Mg(2+) increased; this was not seen with preparations from 30 degrees -acclimatized fish. 3. Part of the Mg(2+)-activated adenosine triphosphatase was inhibited by Na(+) and the amount of inhibition appeared to increase at high acclimatization temperatures. 4. This Na(+)-inhibited adenosine triphosphatase was separated from the (Na(+)+K(+))-activated enzyme by centrifugation on sucrose density gradients. 5. Preparations from 8 degrees -acclimatized fish contained less Mg(2+)-activated and more (Na(+)+K(+))-activated adenosine triphosphatase than did similar fractions from 30 degrees -acclimatized fish. 6. Acclimatization to different environmental temperatures might involve one form of adenosine triphosphatase changing to another. The origin of various membranes seen in microsomal fractions must, however, be established before this hypothesis can be tested further.

Journal Article↗

PubMed1968

Effect of a saline environment on sodium transport by the toad colon.

1. Colons isolated from saline-adapted or aldosterone-injected toads maintained transmural potential differences with the serosal side positive to the mucosa. The short-circuit currents of colons taken from aldosterone-injected toads could be expressed quantitatively by the net flux of sodium measured isotopically. This did not apply to saline-adapted colons where the net sodium flux was from serosa to mucosa.2. The short-circuit currents of colons taken from aldosterone-injected animals increased as the sodium concentration was raised from 10 to 50 mM, then decreased as the sodium concentration was further increased to 115 mM. Adaptation to saline changed this relationship, the short-circuit current becoming directly dependent on the sodium concentration.3. Faecal sodium was higher than serum sodium in saline-adapted toads. There was little or no change in the level of serum sodium or potassium. The urine of saline-adapted toads also contained high concentrations of sodium.4. The total and ouabain-sensitive ATPase activities of mucosal scrapings taken from saline-adapted colons were about half those found in the aldosterone-injected animal. Ten per cent of the total ATPase activity could be inhibited by ouabain.5. Microsomal fractions of mucosal scrapings taken from saline-adapted toads contained 4 times less Na(+) + K(+)-activated ATPase than did corresponding fractions from aldosterone-injected animals. High concentrations of sodium inhibited the microsomal ATPase activity irrespective of the previous conditions of adaptation.6. Regulation of sodium movements across the toad colon appears to be a complex process with the mucosal cells changing their properties so that they either absorb or secrete sodium ions depending on the physiological state of the animal.

Adaptation, Physiological↗

PubMed1968

Interdependence of albumin and sodium transport in the foetal and new-born pig intestine.

1. Everted sacs of new-born pig intestines incubated in bicarbonate saline at 37 degrees C, transferred bovine plasma albumin across the mucosa into fluid bathing the serosa, the amount transferred increasing as the concentration of albumin in the mucosal fluid was raised from 0.5 to 16 g/100 ml.2. The rate of albumin transfer across the foetal pig intestine showed an apparent maximum, about 400 mug/g intestine/hr, 2 weeks before birth. The transfer at birth, about 200 mug/g intestine/hr, fell sharply during the next 2 days but later returned to that previously found at birth.3. When sacs were prepared from the intestines of 1 to 7-day-old pigs part of the recovered albumin was degraded. No digestion was found when the intestines of new-born or foetal pigs were used.4. The transfer of water and sodium, but not glucose, measured across the foetal and new-born pig intestine, was consistently higher when albumin was present in the mucosal fluid: the transmural potential difference was lowered by the presence of albumin. These differences disappeared during the first 2 days of life.5. Both the total and ouabain-sensitive adenosine triphosphatase (ATPase) activities of the pig intestinal epithelium fell within 24 hr of birth. There was some increase in total ATPase activity in older pigs but the ouabain-sensitive activity remained low.6. The relation between albumin and sodium transport, seen at a time when albumin is not being metabolized, suggests that the transfers are closely coupled. The movement of sodium into a mucosal cell down its own concentration gradient may provide energy for the translocation of albumin.

Adenosine Triphosphatases↗

PubMed1968