Flow-mediated K(+) secretion in horses intoxicated with lolitrem B (perennial ryegrass staggers)

To investigate the effects of lolitrem B intoxication on renal K(+) secretion in response to increased tubular flow rates.

Results are derived from a repeated measure pilot study of seven horses fed non-perennial ryegrass feed for a week prior to exposing them to perennial ryegrass seed and hay that contained an average of 2 ppm lolitrem B. At the end of the control and treatment period frusemide (1 mg/kg I/V) was administered and serial fractional excretion of K(+)(FEK(+)) and fractional excretion of Na(+)(FENa(+)) calculated. Baseline concentration of aldosterone in plasma, serum K(+)concentration and feed K(+) concentration were also compared.

Key findings included a reduced change in FEK(+) from 0 to 15 minutes in response to frusemide administration (p=0.022, Wilcoxon signed-rank test) and a reduced baseline concentration of aldosterone in plasma (p=0.022, Wilcoxon signed-rank test) during the treatment period compared with the control.

Results suggest that lolitrem B intoxication reduced flow-mediated K(+) secretion and interfered with aldosterone production or secretion. However, further investigation is required to validate these findings and to further elucidate the underlying pathophysiology.

Lolitrem B intoxication in horses may cause disruption to electrolyte handling in addition to neurological deficits.