Stimulation of ion transport by ascorbic acid through inhibition of 3′:5′-cyclic-AMP phosphodiesterase in the corneal epithelium and other tissues

Please send reprint requests to J. E. Phillips. 1. The unidirectional fluxes of 36Cl− and 22Na+ across short-circuited locust recta bathed in a simple NaCl saline were followed with time. Unidirectional fluxes and net flux of 22Na+ to the haemocoel side all remained constant for at least 4 h and were unaffected by either corpora cardiaca homogenate (CC) or cAMP. 2. Both CC and cAMP stimulated influx and net flux of 36Cl− to the haemocoel side. Over the whole time course of the experiment, i.e. both before and after stimulation, net Cl− flux approximately equalled the shortcircuit current (ISC). 3. Neither CC nor cAMP caused substantial stimulation of ISC or transepithelial electropotential difference (PD) if all Cl− in the bathing saline was replaced by either sulphate or nitrate or acetate. 4. Acetate saline sustains ISC, PD and transepithalial resistance (R) at higher levels than does simple Cl-saline. 5. Experiments with Cl-free, SO4-salines suggest that alternate electrogenic transport processes can be slowly turned on when Cl− is absent, provided a complex saline which contains several organic constituents, or simple acetate saline, is present.

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Cyclic AMP phosphodiesterase activity at the external surface of intact skeletal muscles and stimulation of the enzyme by insulin

Archives of Biochemistry and Biophysics ◽

10.1016/0003-9861(73)90003-9 ◽

1973 ◽

Vol 154 (2) ◽

pp. 510-519 ◽

Cited By ~ 35

Author(s):

Yin-Tak Woo ◽

J.F. Manery

Keyword(s):

Cyclic Amp ◽

Skeletal Muscles ◽

External Surface ◽

Phosphodiesterase Activity ◽

Cyclic Amp Phosphodiesterase ◽

Stimulation Of

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Regulation of adenylate cyclase and cyclic AMP phosphodiesterase by 5-hydroxytryptamine and calcium ions in blowfly salivary-gland homogenates

Biochemical Journal ◽

10.1042/bj2040153 ◽

1982 ◽

Vol 204 (1) ◽

pp. 153-159 ◽

Cited By ~ 16

Author(s):

I Litosch ◽

M Fradin ◽

M Kasaian ◽

H S Lee ◽

J N Fain

Keyword(s):

Salivary Gland ◽

Cyclic Amp ◽

Adenylate Cyclase ◽

Guanine Nucleotides ◽

Cyclase Activity ◽

Adenylate Cyclase Activity ◽

Cyclic Amp Phosphodiesterase ◽

Maximal Stimulation ◽

Increased Activity ◽

Stimulation Of

Salivary-gland homogenates contain 5-hydroxytryptamine-stimulated adenylate cyclase. Half-maximal stimulation was obtained with 0.1 microM-5-hydroxytryptamine in the presence of added guanine nucleotides. Gramine antagonized the stimulation of cyclase caused by 5-hydroxytryptamine. In the presence of hormone, guanosine 5′-[gamma-thio]triphosphate produced a marked activation of adenylate cyclase activity. Stimulation of adenylate cyclase by forskolin or fluoride did not require the addition of guanine nucleotides or hormone. In the presence of EGTA, Ca2+ produced a biphasic activation of cyclase activity. Ca2+ at 1-100 microM increased activity, whereas 2000 microM-Ca2+ inhibited cyclase activity. The neuroleptic drugs trifluoperazine and chlorpromazine non-specifically inhibited adenylate cyclase activity even in the absence of Ca2+. The cyclic AMP phosphodiesterase activity in homogenates was not affected by Ca2+ or exogenous calmodulin. This enzyme was also inhibited by trifluoperazine in the absence of Ca2+. These results indicate that Ca2+ elevates adenylate cyclase activity, but had no effect on cyclic AMP phosphodiesterase of salivary-gland homogenates.

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