Influence of Vasoactive Substances on the Regulation of Cardiac ATP-Sensitive Potassium Channel Activity

BACKGROUND AND OBJECTIVES: It has been known that various vasoactive agents are involved in the regulation of cardiac function through the modification of the K+ channel activities, including the ATP-sensitive K+ channel (KATP). We examined the effects of several vasoactive agents on the cardiac KATP currents in isolated cardiac myocytes. MATERIALS AND METHODS: Ventricular myocytes were isolated from the hearts of ICR mice by enzymatic digestion. The channel currents were recorded by the excised inside-out and cell-attached patch clamp configurations. RESULTS: In the excised inside-out patches, bradykinin (BRK; 1-10 micrometer) and prostaglandin I2 (PGI; 10-50 micrometer) did not affect the channel activities, whereas the vasodilators increased the attenuated channel activities in the presence of 100 micrometer ATP. BRK and PGI in parallel shifted the dose-response curves of ATP (1-1,000 micrometer), and this inhibited the KATP currents to the right. Endothelin (ET-1; 0.1-1 nM) and leukotriene D4 (LTD; 3-10 micrometer) decreased the channel activities immediately after making the inside-out patches. However, the vasoconstrictors did not affect the attenuated channel activities by ATP. In the cell-attached patches, both BRK and PGI increased the channel activities and these effects were markedly attenuated by glibenclamide (50 micrometer). ET-1 and LTD did not affect the baseline channel activities in the cell-attached patches, but they markedly attenuated the dinitrophenol-induced activities. CONCLUSION: It was inferred that certain vasoactive substances are involved in the regulation of cardiac KATP channel activities, and that bradykinin and PGI2 enhance the channel activities, and ET-1 and LTD4 inhibit the channel activities.

The Prognosis and Factors of Neonatal Thyroid Dysfunction

PURPOSE: The function of the neonatal thyroid is affected transiently or consistently by various maternal thyroid diseases, neonatal diseases, drugs, and more as well as thyroid dysgenesis. In this study, we analyzed several factors of neonatal thyroid dysfunction through neonatal screening test and investigated the prognosis. METHODS: From January 1992 to July 1997, we reviewed 66 newborn patients, who showed abnormal thyroid function in neonatal screening test, and analyzed 62 cases except for 3 cases of thyroid dysgenesis and 1 case of TBG deficiency. In the end, we statistically compared the maternal thyroid disease group with umbilical-iodinated disinfection group because the other groups were too small in numbers. RESULTS: Among 62 cases of neonatal thyroid dysfunction, maternal thyroid disease (A) group had 29 cases (46.8%), umbilical-iodinated disinfection (B) group had 22 cases (35.5%), neonatal disease (C) group had 7 cases (11.2%), idiopathic (D) group had 4 cases (6.4%). Group A showed compensated hypothyroidism 79.3%, transient hypothyroidism 13.8% and hyperthyroidism 6.9%, while group B showed compensated hypothyroidism 77.3% and transient hypothyroidism 22.7%. Capillary TSH showed that group B was significantly higher than group A (P<0.05). The serum T4 showed that group B was significantly lower than group A (P<0.05). The incidence of medication showed no significant difference between groups A and B. The duration of normalizing thyroid function showed that group B was significantly longer than group A. CONCLUSOIN: The iodide-containing disinfectant caused transient thyroid dysfunction which was longer and more severe than in the maternal thyroid disease group even though the time of causative exposure differed.

A Case of Band Heterotopia with Lennox-Gastaut Syndrome / 대한소아신경학회지

Band heterotopia is a rare neuronal migration disorder, resulting in epilepsy and mental retardation. Epilepsy in band heteropopia, of which Lennox-Gastaut syndrome constituted about 20%, varied in nature and degree of severity. Band heterotopia can be diagnosed by brain magnetic resonance imaging (MRI), showing another diffuse layer of gray matter underlying the normal-looking cortex with intervening thin rim of white matter. While positron emission tomography (PET) with [18F]-fluorodeoxyglucose revealed glucose uptake similar to the overlying cortex, single photon emission computerized tomography (SPECT) findings of band heterotopia have not been reported. We report a 8-year-old girl who presented with variable types of generalized seizures and mild mental retardation. She was diagnosed as having band heterotopia with Lennox-Gastaut syndrome by MRI and interictal electroencephalogram (EEG) showing immature background and generalized 2 Hz slow spike and wave complexes. Interictal SPECT, using Tc 99m hexamethyl propylenamine oxime (Tc 99m-HMPAO), revealed the same degree of perfusion in both the areas of band heterotopia and the overlying cortex. By using valproate and lamotrigine, she is now in stable condition with a significant decrease in seizure frequency.