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

Abstract

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

METHODS: 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.

RESULTS: 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.

CONCLUSIONS: 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.

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

Keywords:

• lolitrem B
• perennial ryegrass staggers
• horse
• renal
• electrolyte

Acknowledgements

The authors would like to thank Louise and Andrew Scott for the use of their facilities and assistance during the trial and to thank Lester Fletcher for his advice and support. Funding for the research was provided by the New Zealand Equine Trust.

Notes

*Non-peer-reviewed