Die Beeinflussung des Innenohres durch einen experimentellen Insulin-Mangel-Diabetes bei der Ratte
The inner ear in experimental diabetic rats
The studies were performed on a strain of 60 LEW-Han rats. 38 were treated with streptocotocin, 34 became diabetic, proved by the glucose tolerance test. Twenty-two rats were the control animals. The diabetes of the animals was not treated. For more than 12 months weight, blood glucose and auditory function were controlled in the animals being still alive. Auditory function was tested by the pinna-reflex of Preyer for a frequency range between 1,000 and 20,000 cps. Regarding the mean values of frequency, there could be found neither a decrease nor a difference between normal controls and diabetic rats in a substantial amount. Histological examinations of sacrified diabetic rats showed meanwhile the well known changes of kidney with microaneurism, thickened basal lamina, mesangial proliferation and hyalin bodies. The changes in the inner ear, especially in the region of stria vascularis and lamina spiralis ossea to the ganglion cochleae were rather discret, so that a stronger diminuation of auditory function as a consequence of restricted metabolism was also not to expect. There was also detected a loss of ganglion cells in the ganglion spirale, which correlated with aging. There was no clear difference between diabetic rats and normal controls.
The insulin deficiency diabetes causes severe changes of vessels, which were demonstrated in the kidney. In the inner ear however there were no comparable changes, the hearing ability of diabetic rats remained rather normal.