Biomedical subjects

A Aperia

Publications and source records attributed to A Aperia.

At least 55 records · Page 3Linked to original sources

PubMed1997

Rapid development of glomerulosclerosis in diabetic Dahl salt-sensitive rats.

Diabetic nephropathy tends to develop more readily in patients with a family history of hypertension and/or disturbances in sodium transport across the plasma membrane. This prompted us to study the renal effects of diabetes mellitus in a rat strain which is predisposed to develop salt-sensitive hypertension, the Dahl salt-sensitive rat. Diabetes is associated with several aberrations in the renal handling of sodium, such as elevation of tubular Na+, K+ATPase activity. This effect was more pronounced in Dahl salt-sensitive than in Dahl salt-resistant rats. Severe renal lesions, characteristic of the advanced phase of diabetic nephropathy are very rarely observed in rats with streptozotocin diabetes. However, 2 months after induction of diabetes, the Dahl salt-sensitive rats had morphological signs of advanced glomerular disease. The urinary albumin concentration was very high, but did not correlate with the blood pressure. Non-diabetic Dahl salt-sensitive rats as well as Dahl salt-resistant diabetic and non-diabetic rats had little or no signs of glomerular disease and consistently very low urinary albumin concentrations.

Animals↗

PubMed1997

Effect of extreme prematurity on renal dopamine and norepinephrine excretion during the neonatal period.

Dopamine (DA), produced in proximal tubular cells, is believed to be an important intrarenal natriuretic hormone. Experimental studies have shown that the natriuretic effect of DA is less pronounced in the fetal kidney. We have evaluated renal DA and norepinephrine (NE) in the neonatal period, using urinary excretion as an indicator of renally produced/released-catecholamines. In very low-birth-weight infants (25-30 weeks gestational age) there was an increase in urinary DA (pmol/mumol urinary creatine) and NE (pmol/mumol urinary creatinine) from 1 to 13 days postnatal age, despite a decrease in sodium excretion. Urinary NE correlated with plasma NE, whereas plasma DA was undetectable. In summary, NE excretion parallels plasma levels and could reflect the general sympathoadrenal activity, whereas DA is primarily of renal origin. Renal DA and NE increase in the first 2 weeks of life in immature infants. We conclude that the catecholamine system of the human kidney undergoes maturational changes postnatally.

Chromatography, High Pressure Liquid↗

PubMed1997

The dopaminuric response to high salt diet in insulin-dependent diabetes mellitus and in family history of hypertension.

Alterations in the renal dopamine [DA] system have been suggested to contribute to the development of hypertension and diabetic nephropathy. To identify early abnormalities in renal handling of DA and sodium we challenged 16 normotensive patients with uncomplicated insulin-dependent diabetes (IDDM), 18 normotensive nondiabetic subjects with familial borderline hypertension, and 16 healthy controls, 14-29 years old, with a high-sodium diet (HSD). Systolic blood pressure was slightly higher in subjects with familial borderline hypertension than in the other groups on a normal sodium diet (NSD) (P < 0.05). Blood pressure and 24-h urinary measurements were performed on a NSD and after 3 days on a HSD. Twenty-four-hour urinary DA excretion was similar in all groups on NSD. A significant rise in DA excretion was noted after HSD in control subjects (P < 0.01), but not in subjects with a family history of hypertension or with IDDM. Urinary sodium excretion increased in all groups. A correlation between the change in DA and sodium/creatinine ratio after HSD was seen in healthy controls (r = 0.57, P = 0.02) but not in those with familial borderline hypertension (r = 0.18, P = 0.47) or with IDDM (r = 0.40, P = 0.15). A rise in systolic (but not diastolic) pressure was noted only in the IDDM group after HSD (P = 0.02). In conclusion, an impairment in the renal DA and sodium system can be detected early in IDDM and in individuals with familial hypertension. We speculate that this impairment may contribute to the development of hypertension and microvascular disease in both conditions.

Adolescent↗

PubMed1997

Pyelonephritis provokes growth retardation and apoptosis in infant rat renal cortex.

Childhood pyelonephritis is a common cause of renal cortical scarring and hypoplastic kidneys. To understand the mechanisms underlying the cortical lesions, urinary tract infection was induced in three-week-old rats by an intravesical infusion of E. coli, type 06 K13 HL a rat nephropathogenic strain. Four days after infection, histopathological examination showed marked infiltration of leukocytes in the medullary tissue adjoining the calyces and pelvis. In the cortex, signs of inflammation were found only in the cortical zone adjacent to the pelvis. No cells indicative of inflammation were observed in other parts of the cortex. Immunohistochemistry for endogenous proliferating cell nuclear antigen (PCNA) demonstrated a marked decrease in immunoreactivity in proximal tubular (PT) cells. The mitotic response of PT cells, assessed by 3H-thymidine autoradiography, showed a highly significant decrease during the first four days after induction of the infection. Four days after infection, a transient increase in apoptotic cells was observed in cortical cells outside the inflammatory areas. No increase in apoptotic cells was detected in the cortex 10 days after infection. Only a few apoptotic cells were detected in the control kidneys. In conclusion, the data indicate that inhibition of cell proliferation and enhancement of apoptosis may contribute to the renal parenchymal loss after childhood pyelonephritis.

Animals↗

PubMed1997

Inhibition of COMT induces dopamine-dependent natriuresis and inhibition of proximal tubular Na+,K+-ATPase.

The enzyme catechol-O-methyltransferase (COMT), which plays an important role for dopamine metabolism, is abundantly expressed in the kidney. To test whether the natriuretic effects of dopamine may be related to the rate of dopamine metabolism, rats were treated with nitecapone, a peripheral inhibitor of COMT. Nitecapone, given by gavage, induced a highly significant (5.6-fold) increase in sodium excretion, which was associated with an inhibition of the Na+,K+-ATPase activity in both the proximal convoluted and proximal straight tubules (PCT and PST, respectively). These effects were completely abolished if the rats were also treated with a specific dopamine 1 antagonist, SCH 23390. Furthermore, the natriuretic effect of nitecapone was also observed in rats on a high salt diet. The kidney-specific pro-drug to dopamine, glu-dopa, induced a significant, but less pronounced increase in urinary sodium excretion, associated with a dopamine-dependent inhibition of the Na+,K+-ATPase activity in the PCT but not in the PST. Nitecapone and glu-dopa had an additive natriuretic effect. It is concluded that COMT plays an important role in determining the natriuretic effects of the renal dopamine system.

Animals↗

PubMed1997

Protein kinase C in the developing kidney: isoform expression and effects of ceramide and PKC inhibitors.

Protein kinase C (PKC) is a serine/threonine kinase recognized as a key enzyme in signal transduction mechanisms in various biological processes. During development, PKC is involved in the regulation of growth and differentiation. In mature tissue PKC is important for homeostatic functions. We studied PKC with regard to expression and effects on differentiation, growth and apoptosis in the developing kidney. Using in situ hybridization, we demonstrate age-dependent expression of PKC alpha, PKC delta, PKC zeta and PKC lambda during fetal and postnatal kidney development. The endogenous sphingolipid product ceramide, as well as specific PKC inhibitors, disturbed nephron formation and induced apoptosis in organ cultures of E13 kidneys. In primary cell cultures of proximal tubule cells, ceramide and the specific PKC inhibitors induced apoptosis. In conclusion, PKC alpha, PKC delta, PKC zeta and PKC lambda are expressed in an age-dependent pattern during kidney development. Inhibition of PKC disturbs nephron formation, inhibits growth and induces apoptosis in the developing kidney. The findings suggest that PKC plays an important role in regulating normal kidney growth and differentiation.

Animals↗

PubMed1997

PKA-mediated phosphorylation and inhibition of Na(+)-K(+)-ATPase in response to beta-adrenergic hormone.

The activity of Na(+)-K(+)-ATPase can be regulated by hormones that activate adenosine 3',5'-cyclic monophosphate-dependent protein kinase (PKA). Here, using a site-directed phosphorylation state-specific antibody, we show that hormonal regulation of Na(+)-K(+)-ATPase can occur via phosphorylation of Ser-943 on its alpha-subunit. cDNAs coding for wild-type rat Na(+)-K(+)-ATPase and Na(+)-K(+)-ATPase in which the PKA phosphorylation site Ser-943 was mutated to Ala were stably and transiently transfected into COS cells. In COS cells expressing wild-type Na(+)-K(+)-ATPase the beta-adrenergic agonist isoproterenol (1 microM) significantly increased the level of phosphorylation of the alpha-subunit. Phosphorylation was accompanied by a significant inhibition of the enzyme activity, as reflected by a decrease in ATP hydrolysis and 86Rb+ transport. The effect of isoproterenol was reproduced by the PKA activator forskolin used in combination with the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine and was abolished by the specific PKA inhibitor H-89. Okadaic acid, an inhibitor of protein phosphatases 1 and 2A, enhanced phosphorylation and inhibition of Na(+)-K(+)-ATPase induced by isoproterenol. The changes in activity of Na(+)-K(+)-ATPase linearly correlated with the extent of the alpha-subunit of Na(+)-K(+)-ATPase being phosphorylated. When Ser-943 was replaced by alanine, stimulation of the phosphorylation and inhibition of the activity of Na(+)-K(+)-ATPase induced by isoproterenol, alone or in combination with okadaic acid, were not observed. These results indicate that, in intact cells, modulation of the activity of Na(+)-K(+)-ATPase can be achieved by regulation of the state of phosphorylation of Ser-943. Moreover, they provide a biochemical mechanism by which beta-adrenergic agonists can regulate Na(+)-K(+)-ATPase activity.

1-Methyl-3-isobutylxanthine↗

PubMed1997

Regulation of rat Na(+)-K(+)-ATPase activity by PKC is modulated by state of phosphorylation of Ser-943 by PKA.

We have previously shown that the rat Na(+)-K(+)-ATPase alpha 1-isoform is phosphorylated at Ser-943 by protein kinase A (PKA) and at Ser-23 by protein kinase C (PKC), which in both cases results in inhibition of enzyme activity. We now present evidence that suggests that the phosphorylation of Ser-943 by PKA modulates the response of Na(+)-K(+)-ATPase to PKC. Rat Na(+)-K(+)-ATPase alpha 1 or a mutant in which Ser-943 was changed to Ala-943 was stably expressed in COS cells. The inhibition of enzyme activity measured in response to treatment with the phorbol ester, phorbol 12,13-dibutyrate (PDBu; 10(-6) M), was significantly reduced in the cells expressing the Ala-943 mutant compared with that observed in cells expressing wild-type enzyme. In contrast, for cells expressing Na(+)-K(+)-ATPase alpha 1 in which Ser-943 was mutated to Asp-943, the effect of PDBu was slightly enhanced. The PDBu-induced inhibition was not mediated by activation of the adenosine 3',5'-cyclic monophosphate/PKA system and was not achieved via direct phosphorylation of Ser-943. Sp-5,6-DCI-cBIMPS, a specific PKA activator, increased the phosphorylation of Ser-943, and this was associated with an enhanced response to PDBu. Thus the effect of PKC on rat Na(+)-K(+)-ATPase alpha 1 is determined not only by the activity of PKC but also by the state of phosphorylation of Ser-943.

Alanine↗

PubMed1997

Adenylate cyclase-coupled vasopressin receptor activates AQP2 promoter via a dual effect on CRE and AP1 elements.

Vasopressin plays an essential role for the regulation of water balance by activating the collecting duct-specific water channel, aquaporin-2 (AQP2). Here we present evidence that vasopressin may also act as a long-term, transcriptional regulator of AQP2. The studies were performed on LLC-PK1 cells, which normally express V2 receptor (V2R) and which were transfected with a fragment of the human AQP2 promoter. Activation of the adenylate cyclase-coupled V2R in LLC-PK1 cells induced phosphorylation of adenosine 3',5'-cyclic monophosphate (cAMP) responsive element binding protein (CREB) and expression of c-Fos. Binding of these factors to the CRE and AP1 site did, in combination, lead to AQP2 promoter activation. These results establish the role of vasopressin as a regulator of transcription and are the first example of how a message from a highly specific receptor is, via a dual effect of the cAMP signal on CREB and immediate early gene expression, transduced to the transcription of a final target protein with known biological effects.

Adenylyl Cyclases↗

PubMed1996

Phosphorylation by protein kinase C of serine-23 of the alpha-1 subunit of rat Na+,K(+)-ATPase affects its conformational equilibrium.

Phosphorylation of the alpha-1 subunit of rat Na+,K(+)-ATPase by protein kinase C has been shown previously to decrease the activity of the enzyme in vitro. We have now undertaken an investigation of the mechanism by which this inhibition occurs. Analysis of the phosphorylation of recombinant glutathione S-transferase fusion proteins containing putative cytoplasmic domains of the protein, site-directed mutagenesis, and two-dimensional peptide mapping indicated that protein kinase C phosphorylated the alpha-1 subunit of the rat Na+,K(+)-ATPase within the extreme NH2-terminal domain, on serine-23. The phosphorylation of this residue resulted in a shift in the equilibrium toward the E1 form, as measured by eosin fluorescence studies, and this was associated with a decrease in the apparent K+ affinity of the enzyme, as measured by ATPase activity assays. The rate of transition from E2 to E1 was apparently unaffected by phosphorylation by protein kinase C. These results, together with previous studies that examined the effects of tryptic digestion of Na+,K(+)-ATPase, suggest that the NH2-terminal domain of the alpha-1 subunit, including serine-23, is involved in regulating the activity of the enzyme.

Amino Acid Sequence↗

PubMed1996

C-peptide stimulates rat renal tubular Na+, K(+)-ATPase activity in synergism with neuropeptide Y.

This study was performed in order to test the hypothesis that the connecting peptide of proinsulin, C-peptide, might in itself possess biological activity. Renal tubular Na+, K(+)-ATPase, which is a well-established target for many peptide hormones, was chosen as a model. Rat C-peptide (I) was found to stimulate Na+, K(+)-ATPase activity in single, proximal convoluted tubules dissected from rat kidneys. C-peptide increased the Na+ affinity of the enzyme and all subsequent studies were performed at non-saturating Na+ concentrations. C-peptide stimulation of Na+, K(+)-ATPase activity occurred in a concentration-dependent manner in the dose range 10(-8)-10(-6) mol/l. The presence of neuropeptide Y, 5 x 10(-9) mol/l, enhanced this effect and stimulation of Na+, K(+)-ATPase activity then occurred in the C-peptide dose range 10(-11)-10(-8) mol/l. C-peptide stimulation of Na+, K(+)-ATPase activity was abolished in tubules pretreated with pertussis toxin. It was also abolished in the presence of FK 506, a specific inhibitor of the Ca2(+)-calmodulin-dependent protein phosphatase 2B. These results indicate that C-peptide stimulates Na+, K(+)-ATPase activity, probably by activating a receptor coupled to a pertussis toxin-sensitive G-protein with subsequent activation of Ca2(+)-dependent intracellular signalling pathways.

Animals↗

PubMed1996

Incidence of microalbuminuria in children with pyelonephritic scarring.

There is experimental evidence that loss of renal parenchyma results in hyperfiltration in the remnant glomeruli followed by development of glomerulosclerosis. Microalbuminuria, i.e., a urinary albumin excretion rate of 20-200 micrograms/min, is considered to be an early predictor of diabetic glomerulosclerosis. Hypothetically, increased urinary albumin excretion in patients with pyelonephritic scarring may also indicate glomerulosclerosis, with risk for future deterioration of renal function. This study was performed to determine the incidence of increased albumin excretion in children with mild to moderate pyelonephritic scarring, and to relate the information to glomerular filtration rate (GFR; clearance of inulin) and effective renal plasma flow (clearance of para-aminohippuric acid), as well as to the degree of scarring. The functional investigations were performed under water diuresis. Fifty-seven children, aged 1.7-17.9 years, with pyelonephritic renal scarring were included in the study. Nine young healthy adults were used as controls. The GFR was significantly lower in the children with pyelonephritic scarring than in the controls (median 93 ml/min per 1.73 m2, range 48-133 vs. 111 ml/min per 1.73 m2, range 89-121, P < 0.05), and the urine albumin excretion was significantly higher (median 20 micrograms/min per 100 ml GFR, range 0.8-170 vs. 9.2 micrograms/min per 100 ml GFR, range 3.3-21, P < 0.05). An inverse correlation was found between urine albumin excretion and GFR. Increased urine albumin excretion was found in 70% of the children with a GFR below 90 ml/min per 1.73 m2 compared with 41% of the children with a GFR above this level. Increased urine albumin excretion (> 20 micrograms/min per 100 ml GFR) was found in 51% of the children with pyelonephritic scarring, while only 14% had increased age-adjusted serum creatinine concentrations. The high incidence of microalbuminuria in children with pyelonephritic scarring indicates long-term follow-up until the ultimate outcome has been better defined.

Adolescent↗

PubMed1996

Cellular mechanisms for bi-directional regulation of tubular sodium reabsorption.

The molecular mechanisms underlying the regulation of sodium excretion are incompletely known. Here we propose a general model for a bi-directional control of tubular sodium transporters by natriuretic and antinatriuretic factors. The model is based on experimental data from studies on the regulation of the activity of Na+,K+-ATPase, the enzyme that provides the electrochemical gradient necessary for tubular reabsorption of electrolytes and solutes in all tubular segments. Regulation is carried out to a large extent by autocrine and paracrine factors. Of particular interest are the two catecholamines, dopamine and norepinephrine. Dopamine is produced in proximal tubular cells and inhibits Na+,K+-ATPase activity in several tubule segments. Renal dopamine availability is regulated by the degrading enzyme, catechol-O-methyl transferase. Renal sympathetic nerve endings contain norepinephrine and neuropeptide Y (NPY). Activation of alpha-adrenergic receptors increase and activation of beta-adrenergic receptors decrease Na+,K+-ATPase activity. alpha-Adrenergic stimulation increases the Na+ affinity of the enzyme and thereby the driving force for transcellular Na+ transport. NPY acts as a master hormone by synergizing the alpha- and antagonizing the beta-adrenergic effects. Dopamine and norepinephrine control Na+,K+-ATPase activity by exerting opposing forces on a common intracellular signaling system of second messengers, protein kinases and protein phosphatases, ultimately determining the phosphorylation state of Na+,K+-ATPase and thereby its activity. Important crossroads in this network are localized and functionally defined. Phosphorylation sites for protein kinase A and C have been identified and their functional significance has been verified.

Animals↗

PubMed1996

Ontogeny of K+ transport in rat distal colon.

Infants need to retain more K+ than adults to avoid growth retardation. Since the K+ requirements are different in infants (I) and in adults (A), the mechanisms regulating K+ homeostasis should also be different. The colon plays an important role for the regulation of K+ homeostasis. Colonic K+ transport is bidirectional. In this study we have examined the development of colonic K+ transport with special reference to the contribution of different K(+)-transporting pathways. The net colonic K+ uptake, as determined by in vivo perfusion studies and by 86Rb uptake, was significantly higher in I than in A rats. In both I and A colon, approximately 80% of total 86Rb uptake was dependent on vanadate-sensitive P-type adenosinetriphosphatases (ATPases), but the contribution of these different ATPases changes during development. The activity of colonic Na(+)-K(+)-ATPase, measured as ouabain-sensitive Na(+)-dependent ATP hydrolysis and as 86Rb uptake, was lower in I than in A rats. In contrast, the activity of K(+)-ATPases located in apical membrane and measured as ouabain insensitive and SCH-28080 sensitive, as ouabain-sensitive Na(+)-independent ATP hydrolysis, and as 86Rb uptake was significantly higher in I than in A rats. The ratio between apically located K(+)-ATPases and basolateral Na(+)-K(+)-ATPase activities was almost 3.2-fold higher in I than in A colon. We identified with Northern blot the expression of the colonic H(+)-K(+)-ATPase and the Na(+)-K(+)-ATPase alpha-subunits. The alpha-mRNA expression of both ATPases was significantly higher in I than in A rats. The pH and K+ sensitivity of the ouabain-insensitive, SCH-28080-sensitive K(+)-ATPase was the same in I and A colons. In conclusion, the relative activity of apical K+ absorbing ATPases is higher in the I than in the A colon, which should aid infants in retaining K+.

Adenosine Triphosphatases↗

PubMed1996

Development of urinary concentrating capacity: role of aquaporin-2.

The capacity to concentrate urine develops progressively during postnatal life in most mammalian species. Here we have examined whether low expression of the arginine vasopressin (AVP)-activated water channel aquaporin-2 (AQP-2) may be a limiting factor for the concentrating capacity in the infant rats. Urine osmolality in response to 24-h dehydration increased significantly from 10 to 40 days of age. The most rapid increase occurred during the weaning period, i.e., days 15-20. A similar developmental pattern was observed for AQP-2 mRNA levels in the renal medulla. AQP-2 protein levels also increased markedly from day 10 to 40. Immunohistochemistry revealed that AQP-2 was exclusively located in collecting duct principal cells both in infant and adult rats but that the signal was much weaker in infants. To further examine the relationship between urinary concentrating capacity and AQP-2 expression, we treated rats with a single injection of betamethasone, which is known to accelerate maturation in several organs. Twenty-four hours after treatment, there was an increase in urine osmolality, renal medullary AQP-2 mRNA, and AQP-2 protein levels in infant but not in adult rats. A single injection of a specific V2 agonist caused within 6 h significant increase of AQP-2 mRNA in both infant and adult. The expression of the mRNA of three other transporters involved in the concentrating process, medullary Na(+)-K(+)-ATPase alpha-subunit, Na-K-2Cl cotransporter, and epithelial chloride channel also increased during the weaning period and were upregulated by glucocorticoids. We conclude that there is a well-synchronized development of the many of the components that determine the concentrating capacity and that the low expression of AQP-2 is one of the limiting factors for low concentrating capacity in infants.

Aging↗

PubMed1996

Maturation of rat renal tubular response to alpha-adrenergic agonists and neuropeptide Y: a study on the regulation of Na+,K+-ATPase.

Na+,K+-ATPase in tubular cells plays a pivotal role for the regulation of renal sodium excretion. In adult rats the activity of this enzyme is inhibited by natriuretic hormones and stimulated by antinatriuretic hormones. Here we have examined the tubular response to alpha-adrenergic agonists and neuropeptide Y (NPY) in both infant and adult rats. In the adult kidney, alpha-adrenergic agonists and NPY stimulate Na+,K+-ATPase activity via Ca2+-dependent pathways. Oxymetazoline, a selective alpha-adrenergic agonist, and NPY failed to stimulate proximal tubular (PT) Na+,K+-ATPase activity in 10-d-old rats in doses of 10(-8) to 10(-5) M and 10(-8) to 10(-6) M, respectively, but when tubules were incubated simultaneously with both oxymetazoline 10(-8) M and NPY 5 x 10(-9) M, stimulation was observed in both 10- and 40-d-old rat PT. This effect was abolished by FK 506, an inhibitor of Ca2+ and calmodulin-dependent protein phosphatase 2B in both age groups. A23187, a calcium ionophore, stimulated Na+,K+-ATPase in both infant and adult PT, but 10-fold higher doses were required for the infant tubules. The effect of alpha-adrenergic agonists and NPY on free intracellular Ca2+ was studied in PT cells in primary culture. The Ca2+ response to each agent was less pronounced in infant than in adult cells. Preincubation with NPY, which increases Ca2+ influx into the cells, enhanced the response to the alpha-adrenergic agonist in both infant and adult cells. The results support the concept that the systems regulating renal tubular Na+, K+-ATPase and sodium metabolism undergo postnatal maturation.

Adrenergic alpha-Agonists↗

PubMed1995

Na+,K(+)-ATPase in the choroid plexus. Regulation by serotonin/protein kinase C pathway.

In the choroid plexus, the ion pump Na+,K(+)-ATPase regulates the production of cerebrospinal fluid. We now report that incubation of choroid plexus with an activator of protein kinase C, phorbol 12,13-dibutyrate, strongly stimulates the phosphorylation of Na+,K(+)-ATPase and inhibits its activity. Similar effects were obtained with serotonin, which in the choroid plexus stimulates phosphoinositide turnover, thereby activating protein kinase C. Serotonin (10 microM) increased by about 10-fold the amount of phosphorylated Na+,K(+)-ATPase and significantly reduced its activity. Two-dimensional peptide mapping showed comigration of Na+,K(+)-ATPase phosphorylated by either phorbol 12,13-dibutyrate or serotonin in intact cells and by protein kinase C in vitro. These results demonstrate that first messengers can regulate the activity of Na+,K(+)-ATPase through a mechanism involving protein phosphorylation. Moreover, they provide a plausible mechanism for the demonstrated ability of serotonin to decrease cerebrospinal fluid production.

Animals↗

PubMed1995

Expression of protein kinase C isoforms in renal tissue.

PKC plays a central role for the regulation of renal function. PKC consists of a family of isoenzymes. By employing Northern blot techniques we have demonstrated that mRNA transcripts for the classical Ca(2+)-dependent, diacylglycerol-activated isoform alpha, the novel, Ca(2+)-independent isoform delta and the atypical isoform zeta are abundantly expressed in the rat kidney. The novel PKC-epsilon was weakly expressed. The classical PKCs beta I, beta II and gamma could not be detected. The mRNA expression of PKC-delta and -zeta increased with age. The intrarenal localization of PKC-alpha, -delta and -zeta isoforms were studied in the adult kidney using in situ hybridization. In the cortex, the PKC-alpha isoform showed the strongest hybridization signal. PKC alpha, delta and zeta were all distributed in the outer medulla. The PKC-alpha probe detected particularly strong signal in the outer stripe of the outer medulla. Western blot confirmed the presence of the PKC-alpha, -delta and -zeta enzymes in renal tissue. The results show cell-specific and developmentally-dependent expression of three types of PKC isoforms with different responses to diacylglycerol and calcium. The developmental increase of both PKC-delta and PKC-zeta suggests a specific role for these isoforms for the functional regulation of the mature kidney.

Animals↗