Mechanism of Cataract Formation in Thyroparathyroidectomized Dogs.

Abstract

This work was suggested by the reported occurrence of bilateral cataracts in old thyroparathyroidectomized dogs. Symptoms of parathyroid deficiency were simulated in normal dogs while observing the lenses of these dogs by oblique illumination, and, by opthtalmoscopy at a distance, with the aid of atropine. The symptoms of tetany were simulated. These were thought by clinicians of the latter half of the last century to produce cataracts, decreased blood calcium, increased blood phosphate. and an attempted increase in the deposition of calcium. Tetany was induced by the intravenous injection of oil of wormwood, and the subcutaneous injection of strychnine sulphate. In 18 injections, by the first method, we produced some 49 tonic seizures, and a total of 1 hour and 38 minutes of clonic seizure. The two dogs which lived through this treatment were under observation for 3 months. The dogs receiving strychnine, 20 injections resulting in 26 convulsions, were held 2 ½ months for observation. Neither method yielded us a single cataract. We attempted to lower blood calcium by intravenous injection of solutions of sodium oxalate at the level of 30 mg. per kilo, and also Na2H PO4 solutions, in doses varying from 0.386 gm. to 0.690 gm. per kilo. The oxalate was given in 1 dose, while the Na2HPO4 was given in 3 daily portions. The animals lived only 6 days, but, during this time we could discover no indication of cataract formation. To increase blood phosphate we administered NaH2PO4 solution per os at levels from 3.6 to 5.8 gm. per kilo, given as 3 daily portions for 16 days. The Na2HPO4 dogs cited above also had received phosphate. We could detect no cataractous change in the lenses as a result of this treatment.