Control of renal functions in teleost fishes

1998 Fiscal Year Final Research Report Summary

• Project/Area Number: 08660238
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: General fisheries
• Research Institution: Ishinomaki Senshu University
• Principal Investigator: KAKUTA Izuru Ishinomaki Senshu University・School of Science and Engineering Department of Biotechnology・Associated Professor, 理工学部, 助教授 (70221174)
• Project Period (FY): 1996 – 1998
• Keywords: freshwater fish / renal functions / renal blood flow / hormonal control / local changes / blood pressure / cardiac functions / urine flow

Research Abstract

Changes in the number and structure of renal corpuscles , for example, decrease in the ratio in areas of glomerulus to Bowman's capsule were caused in the anterior portion of the kidney 21 days after the exposure to 15OmOsm/kg NaCl solution, while in the posterior renal portion no conspicuous difference from that of the control was found. It was found that physiological and structural changes in the kidney started from the anterior portion.
The glomerular filtration rate (GFR) and urine flow of freshwater fishes, for example, carp and goldfish were highly variable and were influenced by environmental salinity and dissolved oxygen level(hypoxia), administration of anaesthetic materials and metabolic activity. It appears that both renal blood flow and pressure and systematic blood pressure readily influences GFR and urine flow. These changes were regulated mainly by some hormones and bioactive products such as catecholamines, angiotensin-II and prostagrandin E_2. It was also found that changes of renal functions were caused repidly and locally, even if no significant chages were observed in cardiac functions. On the other hand, it was suggested that autonomic nervous control of renal functions (neural regulation of GFR) has long appeared to be of little physiological significance, though there is the possibility that the increase in activity in adrenergic fibers innervating the kidney contributed to the decrease in GFR and urine flow in the fish exposed to stressful conditions such as hypoxia and high salinity.
When fish were forced branchial irrigation with neutralised lOOppm MS-222 solution, HR increased and urine flow decreased immediately. Increased HR and urine flow were also found in the initial post-stress stage. It was also observed that rapid and local changes of blood flow and catecholamines were caused in the kidney of the fish exposed to MS-222 solution. In addition, these changes in the peripheral sites in the kidney were larger than those in central sites.