The Relation Between Seasonal Hyperglycaemia and Thyroid Activity in the Frog (Rana Temporaria)

Abstract

The mean blood-sugar level of frogs killed in the field without previous excitement showed no significant variation between April and October inclusive (38\m=+-\1\m=.\42mg/100 ml.). The resting blood-sugar level at other times of the year, after 2-3 days in captivity, was slightly lower.A marked hyperglycaemic response to excitement could be elicited in the majority of frogs at the spawning season (March) and throughout the summer, while it was only found in April and early May in a few frogs which showed early development of the gonadial fat-bodies. The response was much reduced in September and absent in October.The seasonal occurrence of the hyperglycaemic response paralleled the known cycle of thyroid activity, and a significant correlation was found between the blood-sugar level and thyroid condition in individual excited frogs. A significant response to excitement has been induced in spring, summer and autumn by previous treatment with thyroxine. It is suggested that the thyroid hormone inhibits the destruction of circulating adrenergic compounds.The role of temperature in limiting the hyperglycaemic response is discussed.In an earlier paper [Smith, 1950] attention was drawn to a seasonal variation in the blood-sugar level of frogs (Rana temporaria) which had been in captivity and unfed for 72 hr. In the course of subsequent work, it became apparent that at some seasons the frog showed a marked hyperglycaemic response to handling and shaminjection. This made a re-investigation of seasonal resting blood-sugar levels desirable. At the same time the response to excitement was studied, and in several experiments thyroxine was given in an attempt to induce hyperglycaemia in unresponsive animals. MATERIAL AND METHODSThe majority of the frogs used for the seasonal work were collected in the Wirral Peninsula. In the early months of the year it was not possible to find frogs locally, and they were obtained from a dealer in Staffordshire. These animals were received on the day following their capture and were at once put in a large glass-sided slate tank at approximately atmospheric temperature. Such frogs were not used until they had been in their new surroundings for 24 hr. The frogs used for the experimental induction of hyperglycaemia were all obtained from the dealer and were kept under similar conditions, except that in some cases they were at room temperature (17-20°C), and not at atmospheric temperature (9-11°C). The frogs were not fed while in captivity. Excited and unexcited frogs Frogs which have been termed ' unexcited ' were either freshly caught, or, in the case of already captive animals, were removed from the tank with minimal disturbance and killed immediately. Blood samples from freshly caught, unexcited frogs were

Physiological response of American bullfrog tadpoles to stressor conditions of capture and hypoxia

“…Wang & Chang (1994) found glucose levels varying between 20 and 64mg/dL, and Stefani (1996) values from 48.97 to 55.86mg%. Hutchison & Turkey (1975) determined mean blood glucose levels of 24.5±3.0mg% for Rana pipiens, while Smith (1954) observed in Rana temporaria mean values of 38±1.4mg%. Baseline levels of blood glucose found in the present study varied between 49.33 and 104.33mg/dL (76.07±18.50mg/dL).…”

Factors affecting normal carbohydrate levels in Rana pipiens

“…Anesthesia on Blood Glucose and L,actate It is probable that disturbance of frogs during experimental manipulation results in changes in blood glucose and lactate and liver glycogen. This has occasionally been noted to be true in some other ectothermic vertebrates (Chavin, 1964;Smith, 1954). The purpose of the experiments reported in this section was to evaluate the effects of some common experimental manipulations, including handling, pithing, and induction of anesthesia, upon blood glucose and lactate.…”

“…Although the occurrence of seasonal variations in blood glucose and liver and muscle glycogen has previously been reported for several species of amphibians (Byrne and White, 1975;Mizell, 1965;Smith, 1954), we felt it important to reexamine this important variable in the present study. In addition to examination of this phenomenon in freshly captured Rana pipiens we have attempted to determine whether seasonal changes occur under relatively constant laboratory conditions.…”

“…A number of workers have confirmed a similar seasonal pattern in wild amphibians (Mizell, 1965;Smith, 1954;Hermansen and Jorgenson, 1969), but no agreement exists concerning whether seasonal changes continue in laboratory-acclimated amphibians. Bat-tell (1969) observed monthly differences in blood glucose levels of Ambystoma tigrinum kept in the laboratory under uniform conditions for various periods.…”

Efeitos do Glucagon no metabolismo glicídico de Chrysemys d'orbignyi (Reptilia, Chelonia) sob a influência das variações estacionais

“…E sta correlação entre influência hormonal e estação do ano foi dem onstrada em anfíbios (M iller e Robbins 1954(M iller e Robbins , 1955a(M iller e Robbins , 1955bSmith, 1954).…”