1. Investigación

During pregnancy, maternal erythropoietic expansion and fetal development require greater mobilization of available iron (Fe) stores. These adjustments in Fe metabolism in humans and rodents are largely mediated by the hormone hepcidin (Hepc), which controls the expression of ferroportin (Fpn), a transporter responsible for exporting Fe from stores to extracellular fluid and plasma. These mechanisms based on the regulation of Hepc on the availability of Fe during gestation in healthy mares remain unknown. The objective of this study was to determine the existence of interrelationships among concentrations of Hepc, ferritin (Ferr), Fe, and estrone (E1) and progesterone (P4) in Spanish Purebred mares along the whole gestation. Blood samples were taken from 31 Spanish Purebred mares each month, during 11 months of pregnancy. Fe and Ferr significantly increased and Hepc decreased during pregnancy (P < 0.05). The secretion peak of estrone (E1) was reached in the 5th month and progesterone (P4) between the 2nd and 3rd months of gestation (P < 0.05). Fe and Ferr were weakly positively correlated (r = 0.57; P < 0.05). Fe and Ferr were negatively correlated with Hepc (r = −0.80 and r = −0.67, respectively) (P < 0.05). P4 was positively correlated with Hepc (r = 0.53; P < 0.05). Pregnancy in the Spanish Purebred mare was characterized by a progressive increase in Fe and Ferr and a reduction in Hepc concentrations. E1 was partially responsible for the suppression of Hepc; on the other hand, P4 induced its stimulation during pregnancy in the mare.

In woman and in animal models, estrogens are involved in iron (Fe) homeostasis supporting the hypothesis of the existence of an “estrogen-iron axis”. Since advancing age leads to a decrease in estrogen levels, the mechanisms of Fe regulation could be compromised. In cyclic and pregnant mares, to date, there is evidence linking the iron state with estrogens pattern. Then, the objective of this study was to determine the relationship among Fe, ferritin (Ferr), hepcidin (Hepc) and estradiol-17β (E2) in cyclic mares with advancing age. A total of 40 Spanish Purebred mares of different ranges of age was analyzed: 4–6 years (n = 10), 7–9 years (n = 10), 10–12 years (n = 10), and >12 years (n = 10). Blood samples were obtained on days −5, 0, +5 and + 16 of the cycle. Compared to mares of 4–6 years, serum Ferr was significantly higher (P < 0.01) and Fe significantly lower (P < 0.01) in mares >12 years of age. Hepc was significantly higher in mares >12 years (P < 0.01) than in those 7–9 years of age. E2 levels were higher in mares of 7–9 years (P < 0.01) than in 4–6 and >12 years of age. Fe and Ferr were negatively correlated with Hepc (r = −0.71 and r = −0.02, respectively). E2 was negatively correlated with Ferr and Hepc (r = −0.28 and r = −0.50, respectively), and positively with Fe (r = 0.31). There is a direct relationship between E2 and Fe metabolism, mediated by the inhibition of Hepc in Spanish Purebred mares. The reduction of E2 decreases the inhibitory effects on Hepc, increasing the levels of stored Fe and mobilizing less the free Fe in circulation. Based on the fact that ovarian estrogens participate in changes in the parameters indicative of iron status with age, the existence of an “estrogen-iron axis” in the mares'estrous cycle could be considered. Future studies are required to clarify these hormonal and metabolic interrelationships in the mare.

Equine ventricular repolarisation wave can be influenced by many physiological and pathological factors. T wave abnormalities have been related to a shorter time for ventricular filling, reduced stroke volume, cardiac output and exercise performance in racehorses. The present research performed electrocardiographic recordings in 14 four-year-old male Andalusian horses, when they were untrained and after three months of an aerobic training programme. Leads I, aVF, V10, V1R, V3R, V1L and V3L were used. It was aimed to assess the incidence of abnormal T waves in this breed, according to the criteria of abnormalities established for other equine breeds, to evaluate if the changes induced by training in the T wave are the same that those reported in the athletic heart syndrome in canine and human athletes and, to analyse if the abnormal T waves could have been related to changes in the plasma concentrations of Na, K, and Cl, since these electrolytes are involved in the cardiac electrical processes. It was found out that the incidence of abnormal T waves was quite high in the Andalusian breed, especially in the precordial leads. Moreover, the incidence of abnormal T waves increased in precordial leads and decreased in lead I and aVF after training. The abnormal T waves after training were shorter and had the same voltage, changes which were different to those presented for the athlete’ heart syndrome. The horses with abnormal T waves had higher plasma K concentrations, both before and after training. Plasma Na and Cl concentration at rest decreased after training. Plasma Na concentrations were positively related to T wave duration and negatively to T wave voltage.

Plasma K accumulation during exercise results from the balance between exchange through biological membranes (mainly muscle fibres and erythrocytes), distribution to other tissues and the haemoconcentration. In the present study, the effect of exercise and training on plasma K concentrations and its relationships with other physiological variables have been analysed in two equine breeds. Twenty male Andalusian (AN) and ten Angloarabian (AA) horses, 7 females and 3 males, were subjected to two standardised exercise tests, composed of four workloads, before and after training. Heart rate (HR) was monitored and venous blood was withdrawn at rest, before each exercise level and during recovery. The following parameters were analysed: packed cell volume (PCV), plasma K, lactate (LA) and total protein (TPP). Furthermore, the horses were filmed and three kinematic parameters were studied: stride duration (SD), frequency (SF) and length (SL). Exercise induced an increase in K from 6 and 8 m/sec in AA and AN horses respectively, a steady-state until the end of the exercise and a decrease after 2 min of recuperation. Some interbreed differences existed, with higher K levels in the AN horses, due to the higher relative exercise intensity, stride frequency and haemoconcentration. K was correlated with HR, PCV, TPP, SL, SD and SF. Training caused a decrease in K in AN, but not in AA horses. Plasma K seems to be a good indicator of the physical effort intensity, fitness and training degrees, but it was not related to the magnitude of the glycolytic response to exercise.

El objetivo de este trabajo ha sido describir un sistema de pun-tuación objetivo, a partir de índices de funcionalidad cardiovas-cular y metabólica, que permita la discriminación entre caba-llos según su potencial atlético. Se han estudiado 45 caballosadultos, Pura Raza Española (PRE), machos. Tras un calenta-miento al trote (4 m/s), los animales realizaron un test de ejer-cicio, a velocidades de 5, 6,7y8m/s, cubriendo 1.000 m encada carga de esfuerzo. Se monitoreó la frecuencia cardiaca(FC) y se extrajeron muestras de sangre venosa en reposo,tras el calentamiento, después de cada fase del test y a los 2,4, 6, 8, 10, 15 y 30 minutos de una recuperación activa. Ensangre entera, se determinó la concentración de hemoglobina(HB) y el valor hematócrito (HTO). En plasma, se midieron losniveles de lactato (LA). Los índices de funcionalidad oxidativoshan sido: HBo’ y HTOo’ (HB y HTO a 8 m/s), V150 y VLA2 (ve-locidad a 150 lpm y 2 mmol/L de LA respectivamente), FCLA2(FC a 2 mmol/L de LA) y LA150 (LA a 150 lpm). Como índicesglicolíticos-mixtos, se han considerado: FCmáx (FC máxima),FCo’ (FC a 8 m/s), LAmáx (LA máximo), V200 y VLA4 (veloci-dades a 200 lpm y 4 mmol/L de LA), FCLA4 (FC a 4 mmol/Lde LA) y LA200 (LA a 200 lpm). Los índices que mejor han dis-criminado a los caballos PRE según su nivel de forma físicahan sido VLA2, LA150 y HTOo’ (oxidativos) y FCo’, VLA4 yV200 (glicolíticos-mixtos). VLA2, VLA4 y V200 estuvieron co-rrelacionados positivamente con el potencial físico y FCo’,HTOo’ y LA150, de modo negativo.

In the present review, the authors, based on the multiple functions performed by the liver, analyze the multiple biochemical and hematological changes as an expression of altered liver function in the horse. The liver performs important metabolic functions related to the synthesis, degradation, and excretion of various substances. Modification of these functions can be evaluated and diagnosed by determining serum concentrations of several serum analytes, including enzymes and other endogenous substances. Hepatocellular enzymes, such as sorbitol dehydrogenase-SDH and glutamate dehydrogenase-GLDH, are released following hepatocellular necrosis. Hepatobiliary enzymes, such as γ-glutamyl transferase-GGT, increase in response to necrosis, cholestasis, and other alterations in bile conducts. Serum concentrations of mainly endogenous and exogenous substances that the liver should synthesize or eliminate, such as proteins (albumin and globulins), bile acids, urea, glucose, total and direct bilirubin, and coagulation factors, and fibrinogen should be included in the liver function test profile. The interpretation of laboratory tests of liver function will allow the diagnosis of functional loss of the organ. Some of the analytes considered provide information on the prognosis of liver disease. This review will provide an accurate and objective interpretation of the common biochemical and hematological tests in use in the diagnosis of equine hepatic disease patients, aiding still further the veterinary activity on the applied equine clinical cases.