title: Osmoregulatory defect in adult mice associated with deficient prenatal expression of six2.
abstract: Suboptimal kidney development resulting from a genetic deficit in nephron number can have lifelong consequences that may lead to cardiorenal complications upon exposure to secondary insults in later life. To determine whether the inherited reduced renal reserve compromises the ability to handle osmotic stress in the adult animal, we challenged the heterozygous 3H1 Brachyrrhine (Br/+) mouse, which displays heritable renal hypoplasia associated with reduced embryonic six2 expression, to a solution of 2% NaCl for 5 days or to fluid restriction for 48 h. Blood chemistry, fluid intake, and physiological parameters, including renal measurements, were determined. Systemic hypertonicity by prolonged salt loading led to significant increases in plasma osmolality and plasma Na(+), along with polydipsia and polyuria, with a significant urine-concentrating defect that was resistant to DDAVP treatment in the adult Br/+ mouse compared with wild-type littermates. The Br/+ mouse also developed a significant increase in blood urea nitrogen at baseline that was further elevated when 2% NaCl was given. Fluid restriction for 48 h further enhanced plasma osmolality and plasma Na(+) responses, although the Br/+ mouse was evidently able to produce a small amount of concentrated urine at this time. Hypothalamic c-Fos expression was appropriately activated in the Br/+ mouse in response to both osmotic challenges, indicating an intact central neuroendocrine pathway that was not affected by the lack of congenital six2 expression. Collectively, our results demonstrate impaired osmoregulatory mechanisms consistent with chronic renal failure in the Br/+ mouse and indicate that six2 haploinsufficiency has a direct effect on postnatal fluid and electrolyte handling associated with fluid imbalance.
authors.affiliation: Department of Anatomy, Biochemistry, and Physiology, John A. Burns School of Medicine, University of Hawaii at Manoa, Honolulu, Hawaii, USA. suwit@hawaii.edu
authors.forename: S Jack
authors.initials: SJ
authors.lastname: Somponpun
authors.forename: Brittany
authors.initials: B
authors.lastname: Wong
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Hynd
authors.forename: Benjamin
authors.initials: B
authors.lastname: Fogelgren
authors.forename: Scott
authors.initials: S
authors.lastname: Lozanoff
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D050034:Antidiuretic Agents / Q000008:administration & dosage; D001806:Blood Urea Nitrogen; D003894:Deamino Arginine Vasopressin / Q000008:administration & dosage; D004326:Drinking; D018507:Gene Expression Regulation, Developmental; D057895:Haploinsufficiency; D018398:Homeodomain Proteins / Q000235:genetics; D007031:Hypothalamus / Q000378:metabolism / Q000503:physiopathology; D007671:Kidney Concentrating Ability; D007676:Kidney Failure, Chronic / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D051379:Mice; D008817:Mice, Mutant Strains; D009399:Nephrons / Q000002:abnormalities / Q000187:drug effects / Q000378:metabolism* / Q000503:physiopathology; D038081:Organogenesis; D009994:Osmolar Concentration; D011141:Polyuria / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D012462:Saline Solution, Hypertonic / Q000008:administration & dosage / Q000378:metabolism; D012964:Sodium / Q000097:blood; D017673:Sodium Chloride, Dietary / Q000008:administration & dosage / Q000378:metabolism; D014157:Transcription Factors / Q000172:deficiency* / Q000235:genetics; D014882:Water-Electrolyte Balance / Q000187:drug effects / Q000235:genetics
chemical_list: D050034:Antidiuretic Agents; D018398:Homeodomain Proteins; D016760:Proto-Oncogene Proteins c-fos; D012462:Saline Solution, Hypertonic; C497420:Six2 protein, mouse; D017673:Sodium Chloride, Dietary; D014157:Transcription Factors; D012964:Sodium; D003894:Deamino Arginine Vasopressin