Ontogenetic differences in convulsive action and cerebral uptake of uremic guanidino compounds in juvenile mice.

Guanidinosuccinate (GSA) and methylguanidine (MG) are endogenous, convulsant guanidino compounds which have been shown to be greatly increased in uremic patients. In the present study, we have investigated the age-related differences in convulsive action and cerebral uptake of these compounds in juvenile mice of 7, 14 and 21 days old. An age-dependent decrease was apparent in the severity of the GSA- and MG-induced convulsions and toxicity. Mean latency for the appearance of clonic convulsions increased with increasing age. Two hours following the i.p. injection of GSA or MG in a dose of 250 mg/kg, the resulting brain concentration decreased with increasing age of the animals. This effect was more pronounced in the case of MG. Neither for GSA, nor for MG was this age-dependent effect apparent after 30 min. GSA and MG serum as well as brain concentrations were lower in 21-day-old mice than in 7-day-old ones. However, the brain/serum concentration ratios of GSA and of MG were significantly lower in 21-day-old mice than in 7-day-old ones, indicating that at least part of the difference in brain level can be explained by higher permeability of the immature blood-brain barrier to these uremic guanidino compounds. In addition, brain/serum ratios of GSA in mice of 7 days old and in mice of 21 days old were significantly lower than the ratios of MG in these age groups, indicative of lower overall blood-brain barrier permeability to GSA than to MG.(ABSTRACT TRUNCATED AT 250 WORDS)