Water balance in the Brattleboro rat: single or multiple defects?

Ontogeny of diabetes insipidus in the brattleboro rat: morphological and physiological correlates

Abstract The homozygous Brattleboro rat is a mutant of the Long Evans rat which fails to produce assayable quantities of vasopressin. Somata of supraoptic magnocellular neurons from adult Brattleboro rats are hypertrophied relative to those from normally hydrated adult Long Evans rats. We have investigated, by light microscopic morphometric analysis of immunoperoxidase-labelled vibratome sections, the postnatal growth of magnocellular neurons in normal Long Evans rats, and the relative hypertrophy of these cells in Brattleboro rats. Morphometric analysis of the somata of immunoidentified oxytocinergic and vasopressinergic supraoptic magnocellular neurons from Long Evans rats aged between 1 and 140 days postnatum revealed that their somata increased rapidly in size only after 14 days; a time that coincides with the start of weaning, with a transient increase in serum osmolality, and with the onset of ability to produce hyperosmotic urine. Oxytocin- and vasopressin-containing neurons in Long Evans rats achieved adult dimensions by 45 days postnatum. By contrast, somata of oxytocin neurons in the Brattleboro rat already showed significant hypertrophy relative to those in Long Evans rats at 7 days postnatum; hypertrophy continued until at least 140 days. The hypertrophy in the Brattleboro rat at 7 days was associated with markedly raised serum osmolality relative to that of age-matched Long Evans rats between 1 and 14 days.

Glycosaminoglycans of the rat renomedullary interstitium: ultrastructural and biochemical observations

The rat renal papillary interstitum which contains abundant proteoglycans is a unique area important in renal function. These proteoglycans were studied ultrastructurally by ruthenium red fixation and staining and phosphate-buffered fixation before and after enzyme digestion. A tissue culture of rat renomedullary interstitial cells, the predominant cell of the renal papillary interstitum, was studied for its ability to synthesize proteoglycans and the proteoglycans were then analyzed. Tissue slices of whole rat renal inner medulla were also evaluated for their synthetic ability. In combination, these studies indicate that the dominant glycosaminoglycan is hyaluronic acid. The tissue culture of rat renal medullary interstitial cells synthesized glycosaminoglycans and on analysis, hyaluronic acid was found to be the chief glycosaminoglycan secreted by the renomedullary interstitial cells. Combined with the removal of the proteoglycans from tissue by leech hyaluronidase and testicular hyaluronidase, this suggests that the dominant glycosaminoglycan is hyaluronic acid. Hyaluronic acid is also synthesized by the intact papilla confirming the findings with the tissue culture. However, in addition, sulfated glycosaminoglycans were also synthesized by the intact papilla, presumably the product of the noninterstitial components of the papilla.

Propressophysin is present in neurones at multiple sites in Wistar and homozygous Brattleboro rat brain

Vasopressin (VP) is synthesized as propressophysin, containing also neurophysin (NP) and C-terminal glycopeptide (CPP), within the hypothalamo-neurohypophyseal system (HNS). Recently, VP and NP-immunoreactive cells were demonstrated in other rat brain nuclei. Here we report CPP immunoreactivity in perikarya in these nuclei. Within the homozygous Brattleboro rat, known to be deficient in neuronal VP production, no CPP immunoreactivity was seen in these nuclei. However, intense VP and CPP immunoreactivity was present in solitary cells (52.2 +/- 3.3 per rat) and fibres within the HNS.