Evidence for Phosphatidic Acid as the Sodium Carrier

Hokin, Lowell E.; Hokin, Mabel R.

doi:10.1038/1841068a0

Cited by 101 publications

(29 citation statements)

References 5 publications

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“…Since, as indicated above, it is almost certain that the microsome fraction is composed of fragments of the cytomembrane infoldings, it can be concluded with reasonable certainty that the cytomembrane infoldings are the site of the phospholipid effect. Previous studies showed that acetylcholine stimulated the turnover of phosphatidic acid in cell-free preparations of microsomal membranes from brain tissue and that this stimulated turnover was brought about by the combined action of diglyceride kinase and phosphatidic acid phosphatase (36)(37)(38). Attempts to obtain a similar stimulation of phosphatidic acid turnover in cellfree preparations from the salt gland were unsuccessful.…”

Section: The P R O T E I N and P H O S P H O L I P I D Content Of V Amentioning

confidence: 96%

“…We suggested in a preliminary communication (24) that the increased incorporation of ps, into phosphoinositide on stimulation of salt gland slices with acetylcholine might be a secondary effect consequent to a more rapid turnover and higher specific activity of phosphatidic acid in the stimulated slices. The suggestion was based on the fact that phosphatidic acid appears to be a precursor for the synthesis of phosphoinositide in some systems (52).…”

Section: -5~mentioning

confidence: 99%

“…Diglyceride kinase activity was measured by the radioactive technique described previously (37,38). The only modification in the present experiments was that in some experiments the substrate used was a commercial preparation of diglyeeride which contained diolein as its major component.…”

Section: Distribution Of Diglyceride Kinase and Phosphatidic Acid Phomentioning

confidence: 99%

“…Phosphatidic acid phosphatase was measured as described previously (37), with the modification that phosphatidie acid synthesized chemically from a commercial diolein preparation was used as the substrate.…”

Section: Distribution Of Diglyceride Kinase and Phosphatidic Acid Phomentioning

confidence: 99%

“…Part of this work was presented in a preliminary communication (24) and has been discussed elsewhere in a review (25).…”

mentioning

confidence: 99%

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Studies on the Carrier Function of Phosphatidic Acid in Sodium Transport

Hokin

1960

The Journal of General Physiology

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171

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Incubation of slices of the salt gland of the albatross with acetylcholine, which is the physiological secretogogue for this tissue, led to a 13-fold increase in the rate of incorporation of p3~ into phosphatidic acid and a 3-fold increase in the incorporation of p82 and inositol-2-H 3 into phosphoinositide. The incorporation of p~2 into phosphatidyl choline and phosphatidyl ethanolamine was increased relatively slightly or not at all. Respiration was doubled. The "phospholipid effect" occurred in the microsome fraction, which is known to contain fragments of the endoplasmic reticulum. The enzymes, diglyceride kinase and phosphatidic acid phosphatase, which catalyze the stimulated turnover of phosphatidic acid in brain cortex, were also found in highest concentration in the microsome fraction. The phosphatides which respond to acetylcholine are bound to protein in the membrane. On the basis of these findings it appears that phosphatidic acid and possibly phosphoinositide participate in sodium transport. A scheme, termed the phosphatidic acid cycle, is presented as a working hypothesis, in which the turnover of phosphatidic acid in the membrane, catalyzed by diglyceride kinase and phosphatidic acid phosphatase, functions as a sodium pump. I N T R O D U C T I O NElectrophysiological studies on the i n v e r t e b r a t e a x o n (1, 2), the muscle fibre m e m b r a n e (3), the frog skin (4, 5), a n d other p r e p a r a t i o n s h a v e shown t h a t s o d i u m ions are actively t r a n s p o r t e d against an electrochemical gradient. T h e

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Section: The P R O T E I N and P H O S P H O L I P I D Content Of V Amentioning

confidence: 96%

Section: -5~mentioning

confidence: 99%

Section: Distribution Of Diglyceride Kinase and Phosphatidic Acid Phomentioning

confidence: 99%

Section: Distribution Of Diglyceride Kinase and Phosphatidic Acid Phomentioning

confidence: 99%

“…Part of this work was presented in a preliminary communication (24) and has been discussed elsewhere in a review (25).…”

mentioning

confidence: 99%

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Studies on the Carrier Function of Phosphatidic Acid in Sodium Transport

Hokin

1960

The Journal of General Physiology

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171

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Possible Mechanisms of Active Transport

Wilbrandt

1962

Ciba Foundation Symposium ‐ Enzymes and Drug Action

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Fine structure of the rectal (salt‐secreting) gland of the spiny dogfish, Squalus acanthias

Bulger

1963

Anat. Rec.

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The rectal gland of the spiny dogfish, Squalus acanthias has been described by light and electron microscopy. The cell outline shows remarkable complexity in electron micrographs. The basal plasma membrane has numerous complex infoIdings and interdigitations separated by groups of mitochondria. The lateral plasma membrane also shows extensive interdigitation. The apical region demonstrates profiles of interleafing cell processes with much membrane interdigitation occurring between them but containing few mitochondria. The apical surface has microvilli which extend into the tubular lumen and are covered with nap-like filaments. Glands of some fish were catheterized and attempts were made to correlate the fine structure of these glands with the known secretory rates. The cellular morphology of the secretory cells of the rectal gland correlates well with that seen in other ion-transporting tissues, although some unique specializations were noted.Ion transport pervades all of biology. In spite of efforts by scientists of many fields, the basic mechanisms of ion accumulation and pumping remain unknown. One approach to the problem of salt secretion is to examine the structure of cells which are highly specialized for this activity. The rectal gland of the spiny dogfish, Squalus acanthias, is such a tissue. Burger and Hess ('60a, b ) catheterized the duct of the gland and have shown that this gland was capable of secreting a sodium chloride solution with a concentration about twice that of the blood plasma and greater than that of sea water. They also showed that the volume of fluid excreted was large enough to eliminate significant amounts of sodium chloride from the fish, this presumabIy being its function. Burger ('62) also demonstrated that the gland secreted at a greater rate after the fish received a large dose of salt solution. He could find no evidence of neural control.Important articles from the older literature on the anatomy and physiology of elasmobranch rectal glands were those of Pilliet (1885), Crawford (1899), Hoskins ('17), and Crofts ('25). The recently published physiological studies proposing a salt-excreting function have awakened a new interest in the morphology of this gland. Abstracts have been published on the histochemistry of elasmobranch rectal glands by Bernard and Hartmann ('60) on the histology and ultrastructure of rectal glands from Squalus acanthias by Bulger ('61) and on the ultrastructure of the glands of Urolophus (round sting-ray) by Doyle ('62a). IR addition, Doyle ('6%) recently published an article on the fine structure of the secretory cells of Urolophus with comments on the structure seen in Squalus acanthias.Various structures have been associated with the function of salt secretion, but no unique structure has been identified with certainty as being responsible for salt concentration. Rather, it appears that the rectal gland, in general, resembles the structure, both coarse and fine, of other electrolyte-separating organs. This paper substantiates such a concl...

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Evidence for Phosphatidic Acid as the Sodium Carrier

Cited by 101 publications

References 5 publications

Studies on the Carrier Function of Phosphatidic Acid in Sodium Transport

Studies on the Carrier Function of Phosphatidic Acid in Sodium Transport

Possible Mechanisms of Active Transport

Fine structure of the rectal (salt‐secreting) gland of the spiny dogfish, Squalus acanthias

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