Intestinal effects of carrageenans in the rhesus monkey ( Macaca mulatta)

Abstract

In a study in male and female rhesus monkeys ( Macaca mulatta), the effects of a native form of carrageenan (HMR), derived from Chondrus crispus, have been compared with those of a degraded form (C16) obtained from Eucheuma spinosum. Both types were administered in drinking-water for 7–14 wk. Monkeys given 1 % HMR (providing an intake of about 1·3 g/kg/day) all gained weight and remained in good condition. Occult blood occurred sporadically in the faeces, as was the case in controls. Only minor changes, none attributable to HMR administration, were found in the intestinal tract at autopsy and on microscopic examination. Similar findings were recorded in animals given 1 % HMR for 11 wk and subsequently, after a recovery period of up to 11 wk on tap-water, given escalating daily doses of 50–1250 mg HMR/kg for up to 12 wk. Monkeys given 0·5 or 1·0% C16 solution gained weight, but in those on 2·0% C16 (an intake of approximately 2·9 g/kg/day) weight losses were considerable. All monkeys on C16 lost blood frequently from the intestinal tract and developed some degree of anaemia. Pathological changes seen in the colon ranged from shallow mucosal erosions to ulceration associated with cellular infiltration, granulation tissue in the lamina propria and formation of multiple crypt abscesses. The severity of these effects was dose-dependent, and some reversal was indicated in monkeys given 2% C16 for 14 wk and then allowed to recover on tap-water for 20–24 wk. A marked difference was thus demonstrated between the effects of degraded (C16) and native (HMR) carrageenan in the monkey.