Increase In Sodium Transport Research Articles

Methylation increases sodium transport into A6 apical membrane vesicles: possible mode of aldosterone action.

When isolated apical membrane vesicles prepared from cultured A6 epithelia were incubated in vitro with the methyl donor S-adenosylmethionine, the control rate of amiloride-inhibitable sodium transport was doubled. The methylation inhibitors 3-deazaadenosine and S-adenosyl homocysteine returned the S-adenosyl-methionine-stimulated sodium transport to control levels. Neither these agents nor adenosine affected sodium transport into control vesicles. In vesicles incubated with S-adenosyl-[3H-methyl]methionine, both membrane phospholipids and proteins were labeled, and this labeling was inhibited by deazaadenosine. In vesicles prepared from A6 cells treated with aldosterone, sodium transport was twice the control value and S-adenosylmethionine did not cause any further stimulation of transport. In those vesicles, both lipid and protein methylation were increased. These results suggest that methylation, which increases the rate of amiloride-sensitive sodium transport is involved in the action of aldosterone at the apical membrane level in epithelia.

Effects of hormonal and electrical stimulation of sodium transport on metabolism of toad urinary bladder.

The carbon dioxide produced by toad urinary bladders bathed on their mucosal surfaces by sodium Ringer solution and on their serosal surfaces by modified Leibovitz tissue culture medium was analysed by multiple regression on both sodium transport and time. The fractions contributed by metabolism related to transport and by basal metabolism were assessed, and the extent to which these might vary with time was determined. This analytical method, which improves the accuracy with which suprabasal metabolism is estimated, was used to examine the effects on metabolism of vasopressin, aldosterone, and mucosa-positive voltage-clamping. Vasopressin (0.05 u./ml), which on average increased sodium transport 2.9 times and concurrently increased the rate of carbon dioxide production in these transporting tissues, also altered the carbon dioxide production of non-transporting, amiloride-treated control hemibladders. For each hemibladder the ratio of sodium transported to suprabasal carbon dioxide produced after vasopressin was compared with that observed before vasopressin. Differences between the ratios were much reduced when the carbon dioxide productions of the paired transporting hemibladders were corrected for the effects of vasopressin on basal carbon dioxide production. With such analysis, it was confirmed that vasopressin did not alter the stoichiometry of sodium transport. A 30 mV, mucosa-positive voltage clamp, applied near the peak of the response to vasopressin, further increased both sodium transport and carbon dioxide production. No alterations of the ratio of sodium to suprabasal carbon dioxide were seen under these conditions where the maximal rate of active sodium transport in this tissue must have been approached. Active sodium transport was more than doubled some 4 h after adding aldosterone (10(-7) M). However, the related increase in suprabasal carbon dioxide production was greater than threefold. Therefore, whereas the stimulation resulting from vasopressin and voltage clamping had no effect on the ratio of sodium transported to suprabasal carbon dioxide produced, this ratio was reduced significantly by aldosterone. When the sodium transport of aldosterone-treated bladders was increased further by voltage clamping, the ratio of sodium transported to suprabasal carbon dioxide production remained at the reduced value. Sodium transport was increased by approximately 35% more when aldosterone-treated hemibladders were voltage clamped after vasopressin, the control paired hemibladders being exposed to vasopressin and voltage clamping alone.(ABSTRACT TRUNCATED AT 400 WORDS)

Short-term effect of aldosterone on renal sodium transport and tubular Na-K-ATPase in the rat.

The short-term effect of one single injection of aldosterone on the renal sodium transport on one hand, and the Na-K-ATPase activity on the other hand, was studied in chronic adrenalectomized rats. Sodium transport was estimated by clearances, and Na-K-ATPase was measured in microdissected fragments of the nephron, according to our microtechnique previously described. Five to eight days after adrenalectomy, only 30% of the initial enzyme activity was recovered in the cortical collecting tubule (CCT). Administration of aldosterone completely restored the ATP-ase activity within three hours. Adrenalectomy also curtailed by 20-45% the activity of other nephron segments but aldosterone had no stimulatory effect on them. Sodium-reabsorption also increased after the hormone injection, following the same time (0.5 less than t1/2 less than 1 h) and dose dependencies (0.8 less than K1/2 less than 0.9 micrograms/kg) as those observed for the enzyme activity in the CCT. It is concluded that the short-term stimulation of Na-K-ATPase in the collecting tubule, after an acute administration of aldosterone, may be responsible for the simultaneous increase in sodium transport.

Mineralocorticoid activity of 19-nor-DOC and 19-OH-DOC in toad bladder.

Adrenal enucleation is followed by a period of increased sodium reabsorption thought to be due to excess mineralocorticoid activity. However, it has not been demonstrated that increased production of any known mineralocorticoid accounts for this antinatriuresis. Recently, 19-hydroxydeoxycorticosterone (19-OH-DOC) was found in incubates of regenerating adrenal capsules 3-4 days postenucleation and 19-nordeoxycorticosterone (19-nor-DOC) was identified in the urine of rats with regenerating adrenals. Because it was possible that these hormones might play a role in the sodium retention after adrenal enucleation, we compared the mineralocorticoid activity of these steroids to aldosterone using the toad bladder. Using short-circuit current as a measure of sodium transport, we found that 19-OH-DOC (10(-8) M) had no significant effect on sodium transport. However, 19-nor-DOC (10(-8) M) increased sodium transport to a degree not different from aldosterone (10(-8) M). Furthermore, the onset of action, duration of activity, and inhibition of effect of 19-nor-DOC by spironolactone were not different from that of aldosterone. We conclude that 19-nor-DOC exhibits a significant effect on sodium transport and thus has the potential to play a role in the sodium retention following adrenal enucleation. Under the conditions of these studies, 19-OH-DOC exhibited no effect on sodium transport.

Role of induced proteins in insulin-stimulated sodium transport.

Insulin increases active sodium transport by the toad urinary bladder, an effect that begins with 15 minutes and persists for at least 20 hours. Although pretreatment of bladders with inhibitors of RNA or protein synthesis has no effect on the response to insulin within the first hour, these agents block the long-term component of insulin-stimulated sodium transport. To examine the relationship of protein synthesis to the sustained increase in sodium transport elicited by insulin, we have studied the effects of the hormone upon the incorporation of radioactive amino acids into mucosal cell proteins. There is no detectable effect of insulin on the uptake of aminoisobutyric acid into mucosal cells or on the incorporation of labeled precursors into total protein; however, using a dual-label technique, we find that insulin increases the incorporation of amino acids into specific soluble and plasma-membrane proteins of granular mucosal cells. Insulin has no discernible effect upon the incorporation of amino acids into proteins of mitochondria-rich mucosal cells. Thus the effects of insulin upon sodium transport appear to be the result of two separate mechanisms, (1) a short-term response that is independent of protein synthesis and (2) a long-term response that is expressed after the first hour of hormone treatment and that requires the synthesis of one or more specific proteins in the granular cell.

Epithelial organization and hormone sensitivity of toad urinary bladder cells in culture.

Two continuous cell lines (TB-M and TB-6c) derived from epithelial cells of the toad urinary bladder form epithelia in culture that manifest hormone-sensitive transepithelial transport. Development of transepithelial electrical resistance (R) and transport rate (ISC) are dependent on time and density of cells seeded, but steady-state ISC and R are characteristic for each cell line and independent of seeding density. Some responses of intact toad bladder are preserved in culture, whereas others are altered or absent. Neither cell line responds to vasopressin. Analogues of cAMP increase sodium transport and urea permeability in both cell lines but do not affect water permeability. The intramembrane particle aggregates associated with the vasopressin- and cAMP-induced increase in water permeability of the intact bladder could not be detected in the cell lines. Aldosterone increases sodium transport in both cell lines, and the time course and concentration dependence of the response to aldosterone are similar to those of the intact bladder. The relative effect of a series of steroids on ISC reveals corticosterone to be a more potent mineralocorticoid in cultured cells than in the intact bladder.

A role for endogenous prostaglandins in the short‐circuit current responses to osmolal changes in isolated frog skin

1. Reduction in osmolality of the Ringer solution bathing the morphological inside of frog skin (by lowering the NaCl concentration) caused a significant increase in sodium transport as measured by the short-circuit current. Pretreatment of the skin with acetylsalicylic acid (2.5 x 10(-4)M) abolished the short-circuit current and open-circuit potential responses to osmolal change.2. The output of prostaglandin-like material from isolated frog skin was increased by incubating the skin in hypotonic Ringer solution.3. The cyclic AMP levels of isolated frog skin were also increased by a reduction in the osmolality of the Ringer fluid bathing the skin.4. Prostaglandin-like material was released both by the separated epithelial and dermal layers of frog skin and the output from both layers, on a unit wet weight basis, did not differ.5. The output of prostaglandin-like material from the separated layers of the skin was substantially greater than from whole skin. Indomethacin (6 x 10(-6)M) reduced the output of this material by more than 90% from both layers.6. The release of prostaglandin-like material from the separated layers of the skin was not altered by a reduction in osmolality of the bathing medium.7. It is concluded that a reduction in the osmolality of the solution bathing frog skin stimulates prostaglandin production and that the increased level of prostaglandins stimulates transepithelial sodium transport by stimulating cyclic AMP accumulation. It is also concluded that the response to osmolal change can only occur in intact skin since separation of the epithelial and dermal layers abolished the increase in the release of prostaglandin-like material to osmolal change. The site of the increased prostaglandin production and the exact nature of the stimulus remain to be determined.

Renin stimulation by isoproterenol and theophylline in the isolated perfused kidney

The intrarenal mechanisms of renin release were studied in the isolated perfused rabbit kidney during stimulation by isoproterenol, 0.01 mug/kg per min, and by theophylline, 0.87 mg/kg per min. In the absence of urinary flow during the early stages of perfusion, isoproterenol caused a 17% increase of renal vein serum renin concentration (RVSRC) (P less than 0.001) without changing renal blood flow, renal vascular resistance, or serum potassium. dl-Propranolol, 2.0 mg/kg per min. abolished this isoproterenol-induced renin release. A moderate reduction in perfusion pressure prior to the infusion of isoproterenol resulted in a marked additional stimulation of renin release. Studies during and following ureteral occlusion demonstrated that theophylline stimulates renin release by decreasing renal vascular resistance, whereas the concomitant increase in sodium transport to the macula densa exerted an opposite effect. dl-Propranolol did not affect theophylline-induced renin secretion. It is concluded that single exogenous stimuli may activate more than one intrarenal mechanism simultaneously. Isoproterenol has a direct renin-stimulatory effect on intrarenal beta-adrenergic receptors that may be reinforced by baroreceptor stimulation. Theophylline stimulates renin via a baroreceptor mechanism, with simultaneous renin suppression via a sodium-macula densa effect.

Effects of inhibitors of protein and RNA synthesis on aldosterone-stimulated changes in phospholipid fatty acid metabolism in the toad urinary bladder

The effects of an inhibitor of RNA synthesis, cordycepin, and an inhibitor of protein synthesis, cycloheximide, on aldosterone-induced changes in lipid metabolism and phospholipid fatty acid composition have been studied in the toad urinary bladder. At the concentrations employed, the inhibitors abolish the hormone-induced increases in total lipid synthesis, phospholipid fatty acid specific activities, and weight percentage of phospholipid long-chain polyunsaturated fatty acids as well as blocking the aldosterone-mediated increase in sodium transport.

Effects of purified components of jellyfish toxin ( Stomolophus meleagris) on active sodium transport

Using preparative isoelectric focusing and discontinuous membrane partition chromatography, three fractions which alter sodium transport were isolated from venom of the jellyfish Stomolophus meleagris. A fraction which inhibited sodium transport was partially purified and found to possess a molecular weight of approximately 50,000 and an isoelectric point of 3·30. This component, which appeared to affect active sodium transport at the enzyme level, was also found to produce hemorrhage and necrosis in mice. Two fractions were purified which increased sodium transport in a passive manner and possessed molecular weights of 10,000–50,000, and greater than 300,000, respectively, and have isoelectric points of 4·15 and 5·30. The fraction of 300,000 mol. wt contained most of the toxicity. It is concluded that the immediate pharmacological response to jellyfish toxin possibly is due to components which increase sodium transport, while the apparent delayed response is probably due to a component of the toxin which acts in a cardiotonic, ouabain-like manner.

Calcium release in relation to permeability changes in toad bladder epithelium following antidiuretic hormone.

1. Methods for measuring the release of (45)Ca from isolated urinary bladders of toads (Bufo marinus) pre-loaded with this isotope have been devised. One method allowed separate collection from the mucosal and serosal surfaces of the bladders.2. Reducing the ambient calcium concentration reduced the rate of (45)Ca efflux suggesting that efflux of radiolabel represents calcium exchange.3. Antidiuretic hormone, theophylline and prostaglandin E(1) all increased calcium efflux, while lanthanum and amphotericin were without effect. Cyclic AMP caused only an inhibition of calcium release.4. The increase in (45)Ca efflux due to antidiuretic hormone came exclusively from the mucosal side. Experiments with EGTA suggest that the calcium entering the mucosal solution arises mainly from superficial sites in the mucosal membrane.5. The release of (45)Ca by hormone was not influenced by removal of sodium from the bathing solution. Low pH and amiloride reduced or abolished calcium release to hormone.6. The time course of calcium release from the mucosal surface due to hormone was rapid (commencing between 0.5 and 1.5 min after hormone application). Thus calcium release precedes the increase in sodium transport and hydro-osmotic flow following hormone, and appears to be at least as rapid as cyclic AMP generation in the tissue.7. The relationship between calcium release or exchange and the permeability changes in the bladder to water and to sodium, following hormone, are discussed.

Effect of calcium and vasopressin on the response of frog skin to prostaglandin E1.

1. Prostaglandin E(1) increases sodium transport as measured by short circuit current (SCC) across isolated frog skin whereas calcium, added to the external Ringer fluid, decreases sodium transport. To help establish the site of action of prostaglandin the possible interaction of these two agents on sodium transport has been examined.2. The effect of a standard dose of prostaglandin (0.5 x 10(-6)M) on the short circuit current was tested on paired skins with either zero or high calcium (22.4 mM) in the external Ringer fluid. In ten experiments the responses to prostaglandin (expressed in muA/cm(2)) were not significantly affected by external calcium.3. In another series of experiments the chelating agent, EGTA, was included in calcium-free external Ringer in order to promote greater depletion of skin calcium. The response of these skins to the standard dose of prostaglandin was of the same order of magnitude as that of control skins. The response was not sustained in contrast to that of normal skins and skins in high-calcium fluids.4. In a further series of experiments the reverse procedure was adopted whereby the response of the skin to low and high doses of calcium in the external Ringer was recorded in control conditions and when the skin had responded fully to twice the standard dose of prostaglandin. In addition, the calcium-sensitive current was calculated for each skin in both circumstances. The latter was unchanged on addition of prostaglandin, and graded doses of calcium caused the same degree of inhibition of the short circuit current.5. The results show no interaction between external calcium and prostaglandin and also no need for external calcium in prostaglandin stimulation of sodium transport.6. The findings do not support the concept of chelation by prostaglandin of calcium from critical sites on the skin as the primary mechanism of its action on sodium transport. The results closely parallel those of a similar type of study into the relationship between vasopressin and external calcium on frog skin also.7. When frog skin has responded fully to either prostaglandin E(1) or vasopressin, it shows no response to the other, although removal of calcium from the external Ringer fluid causes a further increase in short circuit current.8. Vasopressin causes a further increase in short circuit current in skins treated with prostaglandin F(1alpha). Prostaglandin F(1alpha) may be a weaker agonist on frog skin than either vasopressin or prostaglandin E(1).

Effect of growth hormone on sodium transport and osmotic water flow across toad skin.

In order to determine the mode by which growth hormone causes sodium and water retention in animals, its action was studied using isolated toad skin. Within minutes, after adding ovine or bovine growth hormone to the medium bathing the inside of the isolated skin, there was an increase in sodium transport and osmotic water movement across the skin. Pretreatment of skins with growth hormone or antidiuretic hormone abolished or reduced stimulation of sodium transport by the other hormone. Similarities between the actions of these two hormones suggested a common mode of action. Demonstration of significant pressor activity in the ovine and bovine growth hormone preparations and lack of stimulation of sodium transport or osmotic water flow across isolated toad skin by highly purified growth hormone lead us to conclude that the sodium and water retaining actions of ovine and bovine growth hormone may be due to contamination with neurohypophysial hormones.

Glucose Metabolism of the Isolated Eccrine Sweat Gland

This paper attempts to further clarify the characteristics of Mecholyl- or epinephrine-stimulated glucose metabolism in the isolated monkey eccrine sweat gland with special emphasis on its relationship to increased sodium transport. The Mecholyl- or epinephrine-stimulated glucose metabolism (as estimated by either lactate or (14)CO(2) production or both) is seen only in the secretory coil and not in the duct. It is markedly suppressed in the absence of glucose, Na(+), or K(+). It is inhibited by ouabain (10(-3) M) and partially suppressed in a low-sodium (40 mM), high-potassium (100 mM) medium.2,4-dinitrophenol (10(-4) M) reverses ouabain-induced inhibition of lactate and (14)CO(2) production but only partially reverses inhibition induced by Na(+) + K(+) deprivation, indicating that metabolic inhibition by ouabain is secondary to the inhibition of sodium transport. There is no synergism between Mecholyl and epinephrine. The absence of any significant inhibitory effects by acetazolamide (Diamox) or HCO(3) (-)-free media suggests that H(+) transport may not be important in sweat gland function. In contrast to a report by Wolfe et al., human eccrine sweat glands show considerable oxidative activity ((14)CO(2) production of 0.42-0.72 nmol/gland/h). These observations are discussed in terms of the linkage between sweat gland energy metabolism and sodium transport.

Effect of β-Adrenergic Catecholamines on Sodium Transport in Turkey Erythrocytes

Abstract Sodium fluxes across the plasma membrane of turkey erythrocytes are 2 to 3 times greater than corresponding fluxes in human erythrocytes. Extracellular potassium stimulates fractional sodium outflux and inhibits sodium influx in turkey erythrocytes. In contrast to human erythrocytes, turkey erythrocytes showed no evidence for sodium-sodium exchange, and at all sodium concentrations studied addition of extracellular potassium inhibited sodium influx. Isoproterenol stimulated accumulation of cyclic adenosine 3':5'-monophosphate (cyclic 3':5'-AMP) and produced a 2- to 4-fold increase in sodium fluxes in turkey erythrocytes. The potency of catecholamine analogs for stimulation of sodium transport correlated directly with their potency for activation of adenylate cyclase in the turkey erythrocyte membrane. Stimulation of sodium transport by isoproterenol is reproduced by adding cyclic 3':5'-AMP to the medium and is blocked by propranolol. The increase in cyclic 3':5'-AMP in response to isoproterenol progresses unimpaired for at least 2 hours. The increase in sodium transport, however, begins to diminish within 30 min after addition of isoproterenol, and after 3 hours of incubation sodium fluxes are only slightly greater than for the control. This phenomenon presumably reflects accumulation of an inhibitor or depletion of a necessary factor for the transport system activated by intracellular cyclic 3':5'-AMP. The rapid effect described here of catecholamines on sodium transport as well as certain results with other systems controlled by hormones through cyclic 3':5'-AMP suggest that endocrine regulation of sodium transport is of general biological significance.

Stretch-induced changes in geometry and ultrastructure of transporting surfaces of toad bladder

Methods were developed for estimation of the area of the microscopic and ultramicroscopic surface of the toad bladder epithelium at various degrees of stretch. Bladder sacs fixed while containing 2.5, 5, 25 or 50 ml of mucosal fluid were studied. For a perfect, hollow elastic sphere, this range of volume corresponds to a sevenfold range of surface area. In the bladder, this increase could be achieved by unfolding of surface irregularities, with no change in surface area, or by stretching the epithelial membrane. The measured microscopic surface area increased threeinstead of sevenfold, but the ultramicroscopic surface remained constant. Thus the bladder stretches (1) by unfolding of the mucosal epithelium, and (2) by flattening of the microvilli. From measurements of the apparent thickness of the mucosal epithelium alone and of the entire bladder, we conclude that the former behaves like a flexible inelastic sheet, whereas the submucosa and serosa stretch elastically. Lateral intercellular spaces do not widen with stretch, but they do become more convoluted because of thinning of the epithelium. Thinning is unlikely to explain the increased sodium transport which follows stretching, because cytoplasmic resistance cannot approach total transepithelial resistance of this preparation.

The stimulation of sodium transport by aldosterone.

Aldosterone, the major sodium retaining hormone in man, will stimulate active transport of sodium across the urinary bladder of the toad, Bufo marinus in vitro , at physiological concentrations of the hormone.The in vitro action of aldosterone is mimicked by steroid hormones with known mineralocorticoid properties and it is competitively inhibited by other analogues, e.g. spironolactone and cortisone. Aldosterone is bound to physiological receptor sites within the transporting epithelial cells, chiefly within the nuclei, and is displaced from these binding sites specifically by structural analogues including other mineralocorticoids. Effects of aldosterone are dependent upon availability of metabolizable substrates to support the active transport of sodium. Although the stimulation of sodium transport by aldosterone can be specifically inhibited by actinomycin D, an inhibitor of RNA synthesis, and by puromycin, an inhibitor of protein synthesis, direct evidence of stimulation of new RNA and protein synthesis during the latent period with physiological concentrations of aldosterone is still lacking. It is possible, however, that the amounts of RNA and protein that are involved are too small to be detected by available techniques. Evidence is summarized which leads us to conclude that the increased sodium transport induced by aldosterone is the consequence of a reduced resistance of the apical plasma membrane of the transporting epithelia to the entry of sodium into the transport pathway.

The effect of valinomycin on the toad bladder: antagonism to vasopressin and aldosterone.

SUMMARY The macrolide antibiotic valinomycin decreased short-circuit current (SCC, Na transport) across the isolated bladder of the toad. This effect was not overcome by increasing the K+ levels in the bathing medium or by the action of amphotericin B. The effects of vasopressin on both sodium and water transfer across the toad bladder were inhibited by valinomycin and the latter inhibition is non-competitive. The action of theophylline in increasing water transfer across the bladder was also inhibited. Cyclic AMP also increased water and Na+ transfer across the bladder but its action was not reduced by the macrolide. These results suggest that valinomycin inhibits adenyl cyclase. Aldosterone increases sodium transport across the toad bladder and this action was abolished by previous incubation of the tissue with the macrolide. Once the steroid-induced effect had been established subsequent addition of valinomycin did not alter the sodium transfer. Valinomycin thus appears to have several sites of action on the toad bladder.

Actions of vasopressin and aldosterone on the toad bladder: inhibition by ethacrynic acid.

SUMMARY Ethacrynic acid inhibited short-circuit current (SCC, Na transport) across the toad bladder. Some structural analogues had similar effects and their potency varied with their ability to combine with SH groups. The Na-K ATPase inhibitor ouabain was more effective than ethacrynic acid and its action and that of ethacrynic acid was additive. The natriferic and hydro-osmotic effects of vasopressin were inhibited by ethacrynic acid (10−5 and 10−4m); the antagonism was competitive at 10− and 10−4 m (but not at 10−3 m). Certain analogues of ethacrynic acid also exhibited this effect but it was not clearly related to their SH-combining ability. The natriferic and hydro-osmotic effects of caffeine and cyclic AMP were not changed by 10−4 m-ethacrynic acid. Ethacrynic acid (10−4 m), which does not affect basal sodium transport in bladders pretreated for studying the action of aldosterone, prevented the initiation of the increase in sodium transport by aldosterone but was without effect when added to a toad bladder already under the influence of aldosterone. This suggests that ethacrynic acid interferes with metabolic processes underlying the action of aldosterone. Dihydroethacrynic acid which has no SH-binding activity was without effect.

Independent action of antidiuretic hormone, theophylline and cyclic 3',5'-adenosine monophosphate on cell membrane permeability in frog skin.

1. The effects of antidiuretic hormone (ADH), theophylline and cyclic 3',5'-adenosine monophosphate (AMP) on membrane potentials in frog skin have been investigated.2. Membrane potentials across the outer and inner facing membranes were recorded in both normal and current clamped skins. In the latter condition active transport of sodium had been abolished by ouabain or metabolic inhibitors, but ionic gradients were maintained by passing current through the skin from the inside.3. ADH increases the potential across the outer facing membranes and reduces the skin resistance. The results are consistent with ADH causing an increase in permeability of the outer facing membranes to sodium ions.4. Theophylline reduces the skin potential by reducing specifically the potential across the outer facing membranes. At the same time the skin resistance is reduced. Theophylline acts by increasing the permeability of the outer facing membranes to chloride ions.5. Cyclic 3',5'-AMP causes a biphasic potential change accompanied by an increase in skin resistance.6. Metabolic inhibitors block the response of the skin to ADH but not to theophylline.7. Separate explanations for the increase in sodium transport by ADH, theophylline and cyclic 3',5'-AMP are discussed. It is not necessary to involve cyclic AMP in order to explain the effects of either ADH or theophylline.