Plasma atrial natriuretic peptide in standardbred and Finnhorse trotters during and after exercise.

To study the exercise-induced changes in atrial natriuretic peptide (ANP), a hormone with cardiovascular and renal effects, an incremental submaximal exercise test on a high-speed treadmill was carried out with Standardbred and Finnhorse trotters, the former bred for speed and the latter originally for heavy work. Standardbreds performed the 2 min exercise intervals at speeds of 6, 7, 8, 9 m s-1 and Finnhorses, according to their training status, at 5, 6, 7, 8 m s-1, 4, 5, 6, 7 m s-1 or 5, 6, 7 m s-1. Steady-state heart rate (HR) was reached within each 2 min interval. The increase in HR was linear and proportional to work intensity and physical condition and it peaked, average 204 beats min-1, during the last speed of the treadmill. Plasma ANP increased significantly and equally, by 27 +/- 4 pg mL-1, in both breeds and peaked at 5 min post-exercise. The rise in ANP during exercise showed good linearity with HR and increasing work intensity. The decrease of ANP after exercise was slow, which may be connected to the regulation of water and electrolytes. Interbreed differences in plasma ANP were not observed. The results suggest a role of ANP in cardiovascular control and fluid balance during and after exercise. In addition to other possible releasing factors during exercise, the increase in HR explains about 40% of the variability in the plasma ANP values.

Influence of medetomidine on acid-base balance and urine excretion in goats.

Seven goats were given medetomidine 5 micrograms/kg as an iv bolus injection. Venous blood samples were taken repeatedly and urine was collected continuously via a catheter up to 7h after the injection. Medetomidine caused deep clinical sedation. Base excess, pH and PCO2 in venous blood rose after medetomidine administration. There were no significant changes in plasma concentrations of sodium, calcium, magnesium, creatinine or osmolality, whereas potassium and bicarbonate concentrations increased, and phosphate and chloride decreased. Medetomidine increased plasma glucose concentration, and in 4 of 7 goats glucose could also be detected in urine. Medetomidine did not influence urine flow rate, free water clearance, bicarbonate and phosphate excretion or pH, but renal chloride, sodium, potassium, calcium, magnesium and creatinine excretion were reduced. The results suggest that the metabolic alkalosis recorded after medetomidine administration is not caused by increased renal acid excretion.

Radiographic evaluation of ossification of the collateral cartilages of the third phalanx in Finnhorses.

Of 462 Finnhorses (age 1-20 years) evaluated and graded (scale 0-5) radiographically for ossification of the collateral cartilages of the 3rd phalanx of the front feet, 22.9% were totally free from sidebones (Grade 0), and 49.1% had minimal or mild ossification (Grade 1 or 2) at the base of 1 or more of the cartilages. Moderate ossification (Grade 3) was present in 10.2% of the horses, whereas ossification was advanced (Grade 4) or extensive (Grade 5) in 17.8%. In most horses > 1 cartilage was affected and 7.6% of the horses had separate centres of ossification in 1 or more of the cartilages. Large sidebones and separate centres of ossification were more common in females than in males (P < 0.001). The incidence of large sidebones was lower in young females (1-3 years) than in mares 4-6 years of age (P < 0.05), but did not increase significantly with age when young horses, 4-6 years of age, were compared with older ones. Grade 4 and 5 sidebones as well as separate centres of ossification were more common in the lateral than in the medial cartilage (P < 0.001), but no difference was observed in this respect between the front feet.