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The cellular localization of increased atrial natriuretic peptide mRNA and immunoreactivity in diabetic rat kidneys
Feng J Lai1, Ming C Hsieh, Shih C Hsin
1Graduate Institute of Medicine, Kaohsiung Medical University, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
Abstract:
Increased intrarenal atrial natriuretic peptide (ANP) mRNA expression has been reported in several disorders. To further investigate the action of renal ANP, we need to elucidate the exact site of its alteration in diseased kidneys. ANP mRNA and ANP were detected by in situ hybridization and immunohistochemistry in the kidneys from five normal and five diabetic rats. Renal ANP mRNA in eight normal and nine diabetic rats was measured by RT-PCR with Southern blot hybridization. In normal and diabetic rats, the distribution of ANP mRNA and ANP-like peptide was mainly located in proximal, distal, and collecting tubules. However, diabetic rats had significant enhancement of ANP mRNA and ANP-immunoreactive staining in the proximal straight tubules, medullary thick ascending limbs, and medullary collecting ducts. ANP mRNA in the outer and inner medulla of nine diabetic rats increased 5.5-fold and 3.5-fold, but only 1.8-fold in the renal cortex. This preliminary study showed that ANP mRNA and ANP immunoreactivity in proximal straight tubules, medullary thick ascending limb, and medullary collecting ducts apparently increased in diabetic kidneys. These findings imply that ANP synthesis in these nephrons may involve in adaptations of renal function in diabetes.
Insights
Diabetic rat kidneys show increased atrial natriuretic peptide (ANP) mRNA and protein in specific tubules. This suggests ANP synthesis in these nephrons may help adapt renal function during diabetes.
Area of Science:
- Nephrology
- Endocrinology
- Molecular Biology
Background:
- Intrarenal atrial natriuretic peptide (ANP) mRNA expression is altered in various kidney disorders.
- Understanding the precise location of ANP changes in diseased kidneys is crucial for elucidating its function.
Purpose of the Study:
- To investigate the specific sites of atrial natriuretic peptide (ANP) alteration in diabetic rat kidneys.
- To determine the role of renal ANP in the adaptation of kidney function during diabetes.
Main Methods:
- In situ hybridization and immunohistochemistry were used to detect ANP mRNA and ANP in normal and diabetic rat kidneys.
- RT-PCR with Southern blot hybridization quantified renal ANP mRNA levels in normal and diabetic rats.
Main Results:
- In diabetic rats, ANP mRNA and ANP-immunoreactive staining were significantly enhanced in proximal straight tubules, medullary thick ascending limbs, and medullary collecting ducts.
- ANP mRNA levels increased substantially in the outer medulla (5.5-fold) and inner medulla (3.5-fold) of diabetic rat kidneys compared to controls.
- A smaller increase (1.8-fold) in ANP mRNA was observed in the renal cortex of diabetic rats.
Conclusions:
- Diabetic kidneys exhibit increased ANP mRNA and immunoreactivity in specific tubular segments, including proximal straight tubules, medullary thick ascending limbs, and medullary collecting ducts.
- These findings suggest that enhanced ANP synthesis in these nephron segments may play a role in the adaptive responses of renal function to diabetes.