Early histochemical changes in irradiated salivary glands and lymph‐nodes of the rat

PLATES CXX-CXXVITHE mechanism by which radiation produces cell injury is unknown.It has been postulated that an initial event may be disruption of intracellular enzyme systems, and this hypothesis has received some support from biochemical work (Alexander and Bacq, 1961).Since cell damage from radiation is focal rather than uniform, histochemical techniques seem particularly suited for further exploring this possibility.In this study we have used these techniques to compare changes produced by radiation in a sensitive tissue with those occurring in relatively resistant tissues.The major salivary glands and lymph-nodes in the neck of the rat were chosen because they represent relatively radioresistant and radiosensitive tissues in close proximity and because the entire complex is accessible to strictly local irradiation. METHODSIn order to minimise damage to other structures a technique was devised for lateral irradiation of the salivary gland-lymph node complex.This was a modification of the method used by Thomlinson (1960, and personal communication) to irradiate tumours in the abdominal wall.A jig was constructed in which a rat could be placed on its side (fig.1).A skin flap containing the salivary glands and lymph-nodes was pulled gently ventrally with a pair of modified artery forceps.Palpation and dissection of the tissues in this position proved that the salivary gland-lymph node complex was pulled with the subcutaneous tissues into the radiation field and away from the trachea, oesophagus and vertebral column.Radiographs also taken in this position confirmed the relation found by dissection (fig.2).The jig with the rat in place was then fixed in the radiation chamber, which is described in full by Thomlinson.Basically this consisted of a Perspex hemisphere with a metal base to which the jig could be bolted.To this chamber air was delivered at 1 litre per min., and the temperature was maintained at 26-30' C. Radiation factorsThe radiation was delivered by a Marconi 250 KV, 15 m.Amp.machine with filters of copper (0.3 mm.) and aluminium (1 mm.).The Perspex top of the radia- tion chamber was 0.5 cm.thick.The half value layer was l .2mm. of copper.The X-rays passed through a 3 cm.hole in a lead shield 4 cm.thick, which collimated