Culture and natriuretic peptide dependent changes in the expression of the natriuretic peptides atrial natriuretic factor (ANF), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP) and the natriuretic peptide receptors A, B, and C in primary cultures of rat proximal tubular cells were demonstrated using polymerase chain reaction analysis and cyclic guanosine monophosphate response to ANF and CNP. Freshly isolated cells expressed mRNA coding for the natriuretic peptide receptor C only, with no expression of the natriuretic peptides or the natriuretic peptide receptors A or B. At confluence natriuretic peptide receptor C expression was lost, while mRNA transcripts for both ANF and BNP and the A and B receptors became apparent. The appearance of mRNA transcripts for the natriuretic peptide receptors A and B during cell growth correspond with a significant increase in the cyclic guanosine monophosphate response to both ANF and CNP, confirming the presence of functionally active guanylate cyclase linked A and B natriuretic peptide receptors. The observed changes in peptide receptor expression during culture were preceded by changes in natriuretic peptide mRNA expression, suggesting the possibility that natriuretic peptide receptor subtype switching may be under the control of endogenous peptide release. Incubation of freshly isolated proximal tubular cells with ANF, BNP, or CNP for 3 h induced similar changes in receptor expression. Incubation with ANF induced expression of the natriuretic peptide receptor B and CNP while inhibiting natriuretic peptide receptor C. Incubation with BNP induced expression of the natriuretic peptide receptor B and CNP. Incubation with CNP induced expression of the natriuretic peptide receptors A and B and CNP. These results suggest that primary cultures of rat proximal tubular cells may experience natriuretic peptide and natriuretic peptide receptor subtype switching as they approach confluence under the control of endogenously expressed natriuretic peptides.

Animals↗

PubMedDate not supplied

Cytokine-stimulated nitric oxide production in the human renal proximal tubule and its modulation by natriuretic peptides: A novel immunomodulatory mechanism?

Although the importance of the human kidney in a variety of disease states is well recognised, the exact mechanisms involved remain unclear. Animal disease models suggest that while high local concentrations of nitric oxide (NO) may play a key role in the initiation and progression of renal disease, low levels may also be essential for normal renal function and cell protection, possibly explaining the variable reports of both beneficial and detrimental responses of renal disease models following NO inhibition. NO has both physiological and pathological roles and clearly a balance between these two primary roles is likely to prevail leading to the conclusion that partial rather than total inhibition of NO production may be beneficial. Despite increasing evidence for the role of NO from animal disease models, little is known of the role of NO and potential modulators within the human kidney. In this review we describe three series of studies during which we examined the ability of primary cultures of human proximal tubular cells to produce NO in response to inflammatory cytokines and the possible role of potential modulators such as the natriuretic peptides. Following challenge with the combination of inflammatory cytokines IL-1beta, TNF-alpha, and IFN-gamma, such cultures exhibit a time-dependent increase in inducible NO synthetase induction and corresponding NO production, an effect which was inhibited by L-NMMA. In the second series of studies we demonstrated that increasing concentrations of atrial natriuretic factor (ANF) or C((4-23))ANF could stimulate a time- and concentration-dependent increase in nitric oxide production which was again abolished by L-NMMA. These results suggested that ANF acting at the natriuretic peptide receptor C could stimulate nitric oxide production in human proximal tubular cells. In the final series of studies we demonstrated that pro-inflammatory cytokine-induced nitric oxide production could be inhibited by ANF, brain natriuretic peptide, C-type natriuretic peptide or C((4-23))ANF. The actions of the natriuretic peptides and C((4-23))ANF was to return pro-inflammatory nitric oxide production to those observed when human proximal tubular cells were incubated with ANF alone indicating that this inhibition was mediated via the natriuretic peptide receptor C. The function of NO in the kidney is unclear but undoubtedly it has both beneficial and detrimental actions which in health remain in balance. However, when the kidney is subjected to an immune challenge, high cytotoxic levels of NO are produced locally and appear to be responsible for local damage, unfortunately total inhibition of NO production during such disease states does not always result in benefit. Clearly total abolition of an NO response removes important integral protective actions such as vasodilation. In the ideal situation, treatment of disease processes related to NO excess would involve the inhibition of these high local levels while still protecting vital dependent mechanisms. We believe that the NO natriuretic peptide interaction, which we have reported in this review, places ANF in a unique position of being able to maintain the essential or protective actions of NO while inhibiting potentially cytotoxic or detrimental effects.

Atrial Natriuretic Factor↗

PubMedDate not supplied

Bilateral inverse Duane's retraction syndrome--a case report.

Duane's retraction syndrome is a well known congenital musculo-facial anomaly. Various explanations have been given for the aetiology of this syndrome. Inverse Duane's retraction syndrome is a condition with reverse clinical features. Abduction of the affected eye is possible to some extent and is accompanied by retraction of the eyeball, narrowing of the palpebral fissure and pseudoptosis. There may be some restriction of movement on adduction. The primary lesion is suspected to be in the medial rectus muscle. Frequently the muscle is found to be entrapped following trauma to the medial wall of the orbit. A case of bilateral inverse Duane's retraction syndrome and convergent squint along with left-sided perceptive deafness is reported. As is usually the case there was no structural abnormality or entrapment of the muscle from trauma.

Adult↗

PubMedDate not supplied

Aminotransferase and amylase activities of subretinal fluid and sera in rhegmatogenous retinal detachment cases.

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Adolescent↗

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Retinal detachment associated with thalassemia major and Marfan's syndrome--a case report.

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Blood Cell Count↗

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Selective antagonism of the AT1 receptor inhibits the effect of angiotensin II on DNA and protein synthesis of rat proximal tubular cells.

The proliferation and hypertrophy of renal tubular cells are primary features in the progression of both acute and chronic renal disease often indicating a poor prognosis. Angiotensin II (ANG II), acting alone or in combination with other growth factors, has been implicated in this process. The aims of this study were to identify the importance of both ANG II and serum-derived factors upon cellular DNA synthesis and protein synthesis in renal proximal tubular cells and to identify the roles of the ANG II receptor subtypes in these processes together with the underlying intracellular signalling mechanisms involved. Primary cultures of renal proximal tubular cells were prepared from freshly isolated rat kidney cortex. Cells were cultured in either serum-replete Dulbecco's modified Eagle's/Ham's F12 or serum-deplete defined medium containing insulin, hydrocortisone, sodium selenite, transferrin, and tri-iodothyronine. Cells were incubated with ANG II (10(-10), 10(-8), 10(-6) M) for 24-120 h either alone or in combination with losartan, PD123319, or pertussis toxin. Incubation of proximal tubular cells in the presence of serum and ANG II (10(-8) M) induced a significant early (24 h) increase in DNA synthesis, together with a significant late (96 h) increase in protein content. [3H]thymidine uptake increased by 56% (p < 0.001) and total protein content by 23% (p < 0.05). In defined media, ANG II (10(-8) M) stimulated protein synthesis only. [3H]uridine uptake, [3H]leucine uptake, and total protein content increased by 25, 57, and 17% (p < 0.05), respectively. In both serum-replete and serum-deplete media, the effects upon protein synthesis of ANG II were inhibited by pertussis toxin and losartan, but not by PD123319. ANG II is clearly a potent stimulator of renal tubular cell DNA and protein synthesis-a response mediated via the AT1 receptor coupled to a pertussis toxin sensitive Gi protein.

Angiotensin II↗