PubMed · 5685795
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M Weller, J Edeiken, P J Hodes. 1968. Renal osteodystrophy.. https://doi.org/10.2214/ajr.104.2.354
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We examined if endogenous endothelins mediate the decreased HCO3 secretion and increased H+ secretion in in vivo-perfused distal tubules of rats fed dietary acid as (NH4)2SO4. Animals given (NH4)2SO4 drinking solution had higher endothelin-1 addition to renal interstitial fluid than those given distilled H2O (480+/-51 vs. 293+/-32 fmol g kidney wt(-1) min(-1), respectively, P < 0.03). (NH4)2SO4-ingesting animals infused with bosentan (10 mg/kg) to inhibit A- and B-type endothelin receptors had higher HCO3 secretion than baseline (NH4)2SO4 animals (-4.7+/-0.4 vs. -2.4+/-0.3 pmol mm(-1) min(-1), P < 0.01), but (NH4)2SO4 animals given a specific inhibitor of A-type endothelin receptors (BQ-123) did not (-2.0+/-0.2 pmol mm(-1) min(-1), P = NS vs. baseline). H+ secretion was lower in bosentan-infused compared with baseline (NH4)2SO4 animals (27.7+/-2.5 vs. 43.9+/-4.0 pmol mm(-1) min(-1), P < 0.03), but that for BQ-123-infused (NH4)2SO4 animals was not (42.9+/-4.2 pmol mm(-1) min(-1), P = NS vs. baseline). Bosentan had no effect on distal tubule HCO3 or H+ secretion in control animals. The data show that dietary acid increases endothelin-1 addition to renal interstitial fluid and that inhibition of B- but not A-type endothelin receptors blunts the decreased HCO3 secretion and increased H+ secretion in the distal tubule of animals given dietary acid. The data are consistent with endogenous endothelins as mediators of increased distal tubule acidification induced by dietary acid.
Although underlying metabolic abnormalities do not differ fundamentally in patients with either first or recurrent nephrolithiasis and 35% of patients with a first event may have to face a recurrence 5 years later, extended metabolic investigations in patients with a first renal calculus should be restricted to particular, exceptional cases. However, in patients with a first calculus basic investigations with respect to specific causes for a concrement such as primary hyperparathyroidism, incomplete renal-tubular acidosis, recurrent urinary tract infection and cystinuria are mandatory. This includes, in addition to a laboratory investigation of blood and urine after a 2-hour-fasting period, analysis of the stone and a urography. The extended metabolic investigation in patients with recurrences or a first occurrence in a patients with a risk constellation includes evaluation of the most important lithogenic (calcium, oxalate, phosphate, uric acid) and inhibiting components (citrate) in the 24-hour urine, in patients with cystine calculi quantitation of cystine. A metabolic investigation should never be undertaken in the hospital or under standardized diet, but always under accustomed, unrestricted nutrition. At least 2 urine samples should be investigated from each patient, preferably not prior to 3-4 months after the event when homeostasis of the patient is restored analogously to the onset of concrement development.
A splice junction mutation at the exon 2-intron 2 boundary of the carbonic anhydrase II (CA II) gene was previously shown to be the unique mutation underlying the CA II deficiency syndrome in patients of Arab descent. Fourteen Tunisian (Maghrebian) families with a history of osteopetrosis, renal tubular acidosis, mental retardation, and CA II deficiency were studied to test the hypothesis that the mutation, found in all 24 patients, derived from a common ancestor originating in the Arabic Peninsula. A filiation study permitted us to trace these families back to a common Arabic tribe that settled in the Maghreb in the tenth century, indicating a common ethnic origin for these families. Segregation of the mutation with a TaqI biallelic restriction site polymorphism upstream of the CA II gene was studied by sequence-tagged site analysis in all the family members. These studies showed cosegregation of the Taq (-) allele with the mutation in 12 families out of 14. This observation supports a founder effect to explain the common CA II deficiency allele in this population. In the remaining two families, a genomic recombination or gene conversion occurred between the TaqI restriction marker and the mutation causing the disease. The relatively high recombination frequency suggests the presence of a hot spot for recombination or gene conversion at the CA II locus.