Increased atrial natriuretic peptide mRNA expression in the kidney of diabetic rats

Abstract

To investigate whether renal synthesis of atrial natriuretic peptide (ANP) is influenced in diabetes, we measured renal ANP mRNA levels, urine volume, urinary ANP and sodium excretion rates in streptozotocin (STZ)-induced diabetic rats. By using reverse transcription-polymerase chain reaction (RT-PCR) followed by Southern blot analysis, we found that renal cortical and outer medullary ANP mRNA levels in untreated diabetic rats were markedly increased as early as the second day after the onset of hyperglycemia and remained elevated for the entire 42-day study period. Plasma ANP concentrations in untreated diabetic rats were increased on the 42nd day, whereas plasma renin activity were suppressed. The urine volume, urinary ANP and sodium excretion rates in untreated diabetic rats were also significantly elevated on the second day and remained elevated for the entire 42-day study period. Urinary ANP excretion rates were well correlated with urine volume, and urinary sodium excretion rate in normal rats and diabetic rats on days 2, 4, 7, 14 and 42. Our results indicate that renal ANP mRNA expression is enhanced in diabetic rats, and that renal-synthesized ANP as one of regulators to handle water and sodium balance in diabetic rats is worthy of further investigation.

Increased C-type natriuretic peptide mRNA expression in the kidney of diabetic rats

“…This method has proved to be reliable for comparing the changes of a gene product in relatively low abundance. Our previous reports demonstrated that renal ANP mRNA is significantly enhanced and the elevation of urinary ANP excretion correlated well with urinary sodium excretion in diabetic rats (Shin et al 1997) and deoxycorticosterone acetate (DOCA)-treated rats (Lee et al 1996). These findings support the proposal that renal-synthesized natriuretic peptide may be related to the change in water-electrolyte balance (Greenwald et al 1991).…”

“…To determine the relative changes in tissue CNP mRNA expression, the yield of CNP PCR products was normalized to the amount of -actin cDNA amplified from the tissue samples. This method has been used in several studies (Lee et al 1996, Shin et al 1997. Experiments were designed to determine the accuracy of the semi-quantitative RT-PCR.…”

“…Using RT-PCR followed by Southern blot analysis, we compared the relative amount of CNP mRNA expression in the renal tissues, a method used in our previous reports (Lee et al 1996, Shin et al 1997. This method has proved to be reliable for comparing the changes of a gene product in relatively low abundance.…”

“…Despite the low expression of ANP gene message in the kidney, by use of reverse transcription-polymerase chain reaction (RT-PCR) we recently demonstrated that renal ANP mRNA levels and urinary ANP excretion rates are markedly increased in diabetic rats (Shin et al 1997). Measurement of urine CNP concentrations (Mattingly et al 1994) and renal CNP mRNA levels (Suzuki et al 1993) has indicated that renal CNP synthesis could be higher than ANP synthesis.…”

The atrial natriuretic peptide (ANP) system in the pronephros and mesonephros of Bufo bufo larvae

“…The vertebrate kidney is an important target organ for ANP; in fact this hormone helps regulate the volume of extracellular fluid and the electrolyte balance by increasing the secretion of water and salt by directly acting on the kidney [23]. Some authors [40][41][42][43][44][45][46] suggest that the mammalian kidney is also involved in the synthesis of the hormone.…”